Method of forming patterns

ABSTRACT

A method of forming patterns includes (a) coating a substrate with a resist composition for negative development to form a resist film, wherein the resist composition contains a resin capable of increasing the polarity by the action of the acid and becomes more soluble in a positive developer and less soluble in a negative developer upon irradiation with an actinic ray or radiation, (b) forming a protective film on the resist film with a protective film composition after forming the resist film and before exposing the resist film, (c) exposing the resist film via an immersion medium, and (d) performing development with a negative developer.

The present application is a Continuation-in-part of U.S. applicationSer. No. 12/895,516, filed on Sep. 30, 2010, which is a Continuation ofU.S. patent application Ser. No. 12/137,232, filed on Jun. 11, 2008,which claims the benefit of Japanese Patent Application No. 2007-155322,filed on Jun. 12, 2007. The entire disclosures of the prior applicationsare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of forming patterns, which isusable in a production process of semiconductors, such as ICs,manufacturing of circuit boards for liquid crystal displays or thermalheads, and other lithography processes of photofabrication. Morespecifically, the invention is concerned with a method of formingpatters by using a resist composition for negative development, aprotective film composition for protecting a film formed from the resistcomposition and a negative developer in the lithography processperforming light exposure by means of immersion-type projection exposureapparatus.

2. Description of the Related Art

As semiconductor devices have become increasingly finer, progress hasbeen made in developing exposure light sources of shorter wavelengthsand projection lenses having higher numerical apertures (higher NAs). Upto now, steppers using as light sources ArF excimer laser with awavelength of 193 nm and having NA of 1.35 have been developed. Asgenerally well known, relationships of these factors to resolution anddepth of focus can be given by the following expressions;

(Resolution)=k ₁(λ/NA)

(Depth of Focus)=±k ₂ ·λ/NA ²

where λ is the wavelength of an exposure light source, NA is thenumerical aperture of a projection lens, and k₁ and k₂ are coefficientsconcerning a process.

As an art of heightening the resolution in an optical microscope, themethod of filling the space between a projection lens and a testspecimen with a liquid having a high refractive index (hereinafterreferred to as an immersion liquid or an immersion medium), or theso-called immersion method, has hitherto been known.

This “immersion effect” can be explained as follows. When the immersionmethod is applied, the foregoing resolution and depth of focus can begiven by the following expressions;

(Resolution)=k ₁(λ₀ /n)/NA ₀

(Focal depth)=±k ₂(λ₀ /n)/NA ₀ ²

where λ₀ is the wavelength of an exposure light source in the air, n isthe refractive index of an immersion liquid relative to the air and NA₀is equal to sine when the convergent half angle of incident rays isrepresented by θ. That is to say, the effect of immersion is equivalentto the use of exposure light with a 1/n wavelength. In other words,application of the immersion method to a projection optical systemhaving the same NA value can multiply the focal depth by a factor of n.

This art is effective on all shapes of patterns, and besides, it can beused in combination with super-resolution techniques under study atpresent, such as a phase-shift method and an off-axis illuminationmethod.

Examples of apparatus utilizing this effect for transfer of fine circuitpatterns in semiconductor devices are disclosed in Patent Document 1(JP-A-57-153433) and Patent Document 2 (JP-A-7-220990), but thesedocuments have no description of resist suitable for immersionlithography.

Recent progress of immersion lithography is reported, e.g., inNon-patent Document 1 (Proc. SPIE, 4688, 11 (2002)), Non-patent Document2 (J. Vac. Sci. Technol., B 17 (1999)), Patent Document 3 (WO2004/077158) and Patent Document 4 (WO 2004/068242). In the case whereArF excimer laser is used as a light source, purified water (refractiveindex at 193 nm: 144) is the most promising immersion liquid in point ofnot only handling safety but also transmittance and refractive index at193 nm, and actually applied in mass production too. On the other hand,it is known that immersion exposure using a medium of a higherrefractive index as immersion liquid can offer higher resolution(Non-patent Document 3: Nikkei Microdevices, April in 2004).

For the purpose of supplementing the sensitivity of resist, which hasbeen reduced by light absorption from the resist for KrF excimer laser(248 nm) onward, the image formation method referred to as a chemicalamplification technique has been adopted as a method of patterningresist. To illustrate an image formation method utilizing chemicalamplification by a positive-working case, images are formed in such aprocess that exposure is performed to cause decomposition of an acidgenerator in the exposed areas, thereby generating an acid, andconversion of alkali-insoluble groups into an alkali-soluble groups byutilizing the acid generated as a reaction catalyst is caused by bakeafter exposure (PEB: Post Exposure Bake) to allow the removal of exposedareas by an alkaline developer.

Since application of immersion lithography to chemical amplificationresist brings the resist layer into contact with an immersion liquid atthe time of exposure, it is pointed out that the resist layer suffersdegradation and ingredients having adverse effects on the immersionliquid are oozed from the resist layer. More specifically, PatentDocument 4 (WO 2004/068242) describes cases where the resists aimed atArF exposure suffer changes in resist performance by immersion in waterbefore and after the exposure, and indicates that such a phenomenon is aproblem in immersion lithography.

As a solution to avoidance of this problem, a method of keeping resistfrom direct contact with water by providing a protective film(hereinafter referred to as a topcoat or an overcoat too) between theresist and a lens is known (e.g., in Patent Documents 5 to 7: WO2004/074937, WO 2005/019937, and JP-A-2005-109146).

In such a method, it is required for the topcoat to have no solubilityin immersion liquid, transparency to light from an exposure light sourceand a property of not causing intermixing with a resist layer andensuring stable coating on the top of a resist layer, and besides, fromthe viewpoint of pattern formation by as-is utilization of an existingprocess, it is preferable that the topcoat has properties of easilydissolving in an alkaline aqueous solution as a developer and allowingremoval simultaneous with removal of a resist layer by development.

However, topcoat-utilized image formation methods hitherto known fail tofully satisfy performance capabilities required for immersionlithography. For example, the pattern formation methods using topcoatshitherto known cause problems of development defects appearing afterdevelopment and degradation in line edge roughness, and they are in needof improvements.

At present, an aqueous alkali developer containing 2.38 mass % of TMAH(tetramethylammonium hydroxide) has broad use as developers for g-ray,i-ray, KrF, ArF, EB and EUV lithographic processes.

As a developer other than the aqueous alkali developer, the developerused for performing development by dissolving exposed areas of a resistmaterial reduced in molecular weight through cleavage of its polymerchains upon irradiation with radiation, and that characterized by havingat least two functional groups of more than one kind chosen from anacetic acid group, a ketone group, an ether group or a phenyl group anda molecular weight of 150 or above, is disclosed, e.g., in PatentDocument 8 (JP-A-2006-227174). In addition, the developers used forperforming development by dissolving exposed areas of specified resistmaterials containing fluorine atoms and chosen from supercriticalfluids, halogenated organic solvents or non-halogenated organic solventsare disclosed in Patent Document 9 (JP-T-2002-525683, the term “JP-T” asused herein means a published Japanese translation of a PCT patentapplication) and Patent Document 10 (JP-T-2005-533907).

However, as the semiconductor devices become finer, it becomesexceedingly difficult to find combinations of, e.g., a resistcomposition, a developer and a protective film (topcoat) compositionappropriate to formation of patterns with synthetically good quality,and it is required to find pattern formation methods which can achieve,e.g., reduction in development defects appearing after development andsatisfactory line edge roughness and can be applied suitably totopcoat-utilized immersion lithography.

SUMMARY OF THE INVENTION

The invention aims to solve the aforesaid problems and to provide apattern formation method which allows not only reduction in developmentdefects appearing after development but also reduction in line edgeroughness and ensures consistent formation of high-accuracy finepatterns for fabrication of high-integration, high-precision electronicdevices.

The following are aspects of the invention, and thereby the aforesaidaims of the invention are achieved.

<1> A method of forming patterns, comprising:

(a) coating a substrate with a resist composition for negativedevelopment to form a resist film, wherein the resist compositioncontains a resin capable of increasing the polarity by the action of theacid and becomes more soluble in a positive developer and less solublein a negative developer upon irradiation with an actinic ray orradiation,

(b) forming a protective film on the resist film with a protective filmcomposition after forming the resist film and before exposing the resistfilm,

(c) exposing the resist film via an immersion medium, and

(d) performing development with a negative developer.

<2> The method of forming patterns of <1>, wherein

the negative developer in the process (d) of performing developmentcontains an organic solvent.

<3> The method of forming patterns of <1>, wherein

the process (d) of performing development comprises a process ofremoving the protective film composition and soluble portions of theresist film at the same time.

<4> The method of forming patterns of <1>, further comprising:

(e) performing development with a positive developer.

<5> The method of forming patterns of <1>, wherein the protective filmhas a rate of dissolution into the negative developer in a range of 1nm/sec to 300 run/sec.

<6> The method of forming patterns of <1>, wherein

the protective film composition contains a resin having at least eithera fluorine atom or a silicon atom.

<7> The method of forming patterns of <1>, wherein

the protective film composition contains a solvent different from thenegative developer.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is schematic diagrams showing relations of exposure amounts topositive development and negative development according to methods inrelated art, respectively;

FIG. 2 is a schematic diagram illustrating a pattern formation methodwhich utilizes a combination of positive development and negativedevelopment; and

FIG. 3 is a schematic diagram showing a relation of exposure amounts tothe positive development and negative development.

DETAILED DESCRIPTION OF THE INVENTION

Best modes for carrying out the invention are described below.

Incidentally, the term “group (atomic group)” used in this specificationis intended to include both unsubstituted and substituted ones whenneither a word of substituted nor a word of unsubstituted is addedthereto. For instance, the term “an alkyl group” is intended to includenot only an alkyl group having no substituent (an unsubstituted alkylgroup) but also an alkyl group having a substituent or substituents (asubstituted alkyl group).

To begin with, explanations for terms used in this specification aregiven. There are two modes of pattern formation, a positive mode and anegative mode, and both modes utilize a change caused in developersolubility of resist film by chemical reaction for which irradiationwith light acts as a trigger, and more specifically, a case whereirradiated portions dissolve in a developer is referred to as thepositive mode, and a case where non-exposed portions dissolve in adeveloper is referred to as the negative mode. As to developers usedtherein, there are two types of developers, a positive developer and anegative developer. The term “positive developer” is defined as adeveloper allowing selective dissolution and removal of portions givenexposure amounts (which are shown by a dotted line in FIG. 1) above acertain threshold value as shown by a solid line in FIG. 1, while theterm “negative developer” is defined as a developer allowing selectivedissolution and removal of portions given exposure amounts below theaforementioned certain threshold value. The development process using apositive developer is referred to as positive development (or a positivedevelopment process too), and the development process using a negativedeveloper is referred to as negative development (or a negativedevelopment process too). The term multiple development (or a multipledevelopment process) refers to the development mode utilizing acombination of the development process using a positive developer andthe development process using a negative developer. In the invention, aresist composition used in negative development is referred to as aresist composition for negative development, and a resist compositionused in multiple development is referred to as a resist composition formultiple development. The simple wording “a resist composition” as usedhereinafter indicates a resist composition for negative development. Theterm “a rinse liquid for negative development” means a rinse liquidwhich contains an organic solvent and is used in a cleaning processafter a negative development process. The term “a protective filmcomposition” (referred to as a topcoat composition too) means a resincomposition capable of forming a protective film (referred to as atopcoat too) which is insoluble in water and can be peeled off,preferably with a negative developer.

As an suitable art for a topcoat process in immersion lithography, theinvention provides a new method of pattern formation utilizing acombination of (a) a process of coating a substrate with a resistcomposition for negative development which contains a resin capable ofincreasing the polarity by the action of an acid to form a film tobecome more soluble in a positive developer (preferably an alkalideveloper) and less soluble in a negative developer (preferably anorganic developer) upon irradiation with an actinic ray or radiation,(b) a process of forming a protective film on the resist film with aprotective film composition after forming the resist film and beforeexposing the resist film, (c) a process of performing immersion exposureof the resist film protected by the protective film and (d) a negativedevelopment process using a developer (a negative developer) whichallows selective dissolution and removal of portions given exposureamounts below a specified threshold value (b) as shown in FIG. 3.

It is preferable that the present method of pattern formation furtherhas (e) a process of performing development with a positive developer.

It is also preferable that the present method of pattern formationfurther has (f) a heating process after the immersion exposure process(c).

In the present method of pattern formation, the immersion exposureprocess (c) can be repeated two or more times.

In the present method of pattern formation, the heating process (f) canalso be repeated two or more times.

Requirements for carrying out the invention include (i) a resistcomposition for negative development which contains a resin capable ofincreasing the polarity by the action of the acid and becomes moresoluble in a positive developer and less soluble in a negative developerupon irradiation with an actinic ray or radiation, (ii) a negativedeveloper (preferably an organic developer) and (iii) a protective filmcomposition forming a protective film insoluble in an immersion medium(preferably water).

For performing the invention, it is favorable that (iv) a positivedeveloper (preferably an alkali developer) is further used.

For performing the invention, it is also favorable that (v) an organicsolvent-containing rinse liquid for negative development is furtherused.

The resist composition for negative development as used in the inventionis a resin composition containing a resin capable of increasing thepolarity by the action of an acid and forming a film which becomes moresoluble in a positive developer and less soluble in a negative developerupon irradiation with an actinic ray or radiation. Therefore, thepresent resist composition for negative development can be used suitablyfor pattern formation through multiple development utilizing acombination of a developer (a positive developer) allowing selectivedissolution and removal of portions given exposure amounts above aspecified threshold value (a), a developer (a negative developer)allowing selective dissolution and removal of portions given exposureamounts below a differently specified threshold value (b) and a resistcomposition for negative development.

More specifically, when pattern elements on an exposure mask areprojected onto a wafer coated with a resist film with irradiation withlight, as shown in FIG. 3, a pattern with resolution equivalent todouble the spatial frequency of the optical image (light intensitydistribution) can be formed through selective dissolution and removal ofregions irradiated with light of high intensities (resist portions givenexposure amounts above the specified threshold value (a)) by use of apositive developer and selective dissolution and removal of regionsirradiated with light of low intensities (resist portions given exposureamounts below the specified threshold value (b)) by use of a negativedeveloper.

When the pattern formation process using two types of developers, apositive developer and a negative developer, is carried out, thesequence of these developments has no particular restriction, and morespecifically, it is appropriate that development be carried out usingeither a positive developer or a negative developer after exposure isperformed, and then negative or positive development be carried outusing a developer different from the developer used in the firstdevelopment. And it is preferable that, after the negative development,cleaning with an organic solvent-containing rinse liquid for negativedevelopment is carried out. By the cleaning with a rinse liquidcontaining an organic solvent after negative development, moresatisfactory pattern formation becomes possible.

The pattern formation method for carrying out the invention is describedbelow in more detail.

<Method of Pattern Formation>

The present method of pattern formation include the following processes.It is preferred that these processes be included in the order asdescribed below.

More specifically, the present method of pattern formation ischaracterized by including sequentially:

(a) a process of coating a substrate with a resist composition fornegative development to form a resist film, wherein the resistcomposition contains a resin capable of increasing the polarity by theaction of the acid and becomes more soluble in a positive developer andless soluble in a negative developer upon irradiation with an actinicray or radiation,

(b) forming a protective film on the resist film with a protective filmcomposition after forming the resist film and before exposing the resistfilm,

(c) a process of exposing the resist film via an immersion medium, and

(d) a process of performing development with a negative developer.

It is preferred that the present method of pattern formation furtherinclude (e) a process of forming a resist pattern by performingdevelopment with a positive developer. By including this process, apattern with resolution equivalent to double the spatial frequency canbe formed.

The process (a) of a coating a substrate with a resist composition fornegative development, which contains a resin capable of increasing thepolarity by the action of the acid and becomes more soluble in apositive developer and less soluble in a negative developer uponirradiation with an actinic ray or radiation, may be performed using anymethod as long as it allows coating a substrate with the resistcomposition. Examples of such a method include coating methods hithertoknown, such as a spin coating method, a spraying method, a rollercoating method and a dip coating method. For applying a coating ofresist composition, a spin coating method is preferable to the others.After application of a coating of resist composition, the substrate isheated (pre-baked) as required. By this heating, it becomes possible toevenly form the coating from which undesired residual solvents areeliminated. The pre-bake temperature has no particular limitations, butit is preferably from 50° C. to 160° C., far preferably from 60° C. to140° C.

The substrate on which resist film is formed has no particularrestrictions in the invention, and it is possible to use any ofinorganic substrates made from silicon, SiN, SiO₂ and the like,coating-type inorganic substrates including SOG, and substratesgenerally used in lithographic processes for production ofsemiconductors, such as ICs, and circuit boards of liquid crystaldisplays, thermal heads and the like, and photofabrication of otherdevices.

Before the resist film is formed, the substrate may be coated with anantireflective film in advance.

As the antireflective film, any of inorganic ones formed from titanium,titanium oxide, titanium nitride, chromium oxide, carbon and amorphoussilicon, respectively, and organic ones formed from, e.g., a combinationof a light absorbent and a polymeric material can be used. In addition,commercially available organic antireflective films including DUV-30series and DUV-40 series manufactured by Brewer Science Inc., AR-2, AR-3and AR-5 manufactured by Shipley Company, and ARC series, such asARC29A, manufactured by Nissan Chemical Industries, Ltd. can also beused.

There is no particular restriction on a resist composition which can beused in the invention so long as the composition contains a resincapable of increasing the polarity by the action of the acid and becomesmore soluble in a positive developer and less soluble in a negativedeveloper upon irradiation with an actinic ray or radiation, but it ispreferred that the composition be usable in exposure to light withwavelengths of 250 nm or shorter, and it is far preferred that thecomposition be usable in exposure to light with wavelengths of 200 nm orshorter. Examples of such a composition include compositions containingresins having alicyclic hydrocarbon groups as illustrated hereinafter.

After the resist film formation process (a), and that before theexposure process (c) performed via an immersion medium, the process (b)is carried out where a protective film (hereinafter referred to as “atopcoat” too) is formed on the resist film by use of a protective filmcomposition. In the process (b), a topcoat is provided between theresist film and the immersion liquid so that the resist film is notbrought to direct contact with the immersion liquid. Properties requiredfor functionality of the topcoat include suitability for coating theresist film, transparency to radiant rays, notably radiation of 193 nm,and poor solubility in an immersion liquid (preferably water). And it ispreferred that the topcoat cause no mixing with the resist and beapplicable evenly to the upper resist layer.

In order to apply a protective film evenly to the top of the resist filmwithout dissolving the resist film, it is preferred that the protectivefilm composition contain a solvent in which the resist film isinsoluble. And it is far preferred that a solvent different from aconstituent solvent of the negative developer as described hereinafterbe used as the solvent in which the resist film is insoluble. Theprotective film composition has no particular restriction as to thecoating method thereof. For example, it can be applied by use of a spincoating method.

In point of transparency to 193 nm, the protective film compositionpreferably contains a resin having no aromatic groups, specifically aresin containing at least either a fluorine atom or a silicon atom asmentioned hereinafter. However, there is no particular restriction onthe resin so long as it can be dissolved in a solvent in which theresist film is insoluble.

The thickness of the topcoat has no particular limitations, but thetopcoat is formed so that the thickness thereof is generally from 1 nmto 300 nm, preferably from 10 nm to 150 nm, in point of transparency toan exposure light source used.

After formation of the topcoat, the substrate is heated as required.

From the viewpoint of resolution, it is preferred that the topcoat havea refractive index close to that of the resist film.

The topcoat is preferably insoluble in an immersion liquid, farpreferably insoluble in water.

As to the receding contact angle of the topcoat (protective film), it isappropriate from the viewpoint of an ability to follow an immersionliquid that the receding contact angle (at 23° C.) of an immersionliquid with respect to the protective film be from 50 degrees to 100degrees, preferably from 60 degrees to 80 degrees. And it is preferablethat the receding contact angle (at 23° C.) of water with respect to theprotective film be from 50 degrees to 100 degrees, particularly from 60degrees to 80 degrees.

In the immersion exposure process, it is required for the immersionliquid to move over a wafer while following the movement of an exposurehead for scanning the wafer at a high speed to form an exposure pattern.Therefore, the contact angle of an immersion liquid in a dynamic statewith respect to the topcoat becomes important and, for achievement ofbetter resist performance, it is appropriate that the receding contactangle be within the range specified above.

For stripping off the topcoat, a negative developer may be used, or astripping agent may be used separately. As the stripping agent, asolvent low in permeability into the resist is suitable. In point ofpossibility of performing the stripping-off process simultaneously withthe resist development process, it is advantageous for a negativedeveloper (preferably an organic solvent) to be able to strip off thetopcoat. The negative developer used for the stripping has no otherparticular restrictions so long as it allows dissolution and removal oflow exposure portions of the resist, and it can be selected fromdevelopers containing polar solvents, such as ketone solvents, estersolvents, alcohol solvents, amide solvents and ether solvents, ordevelopers containing hydrocarbon solvents. Of these developers, thosecontaining ketone solvents, ester solvents, alcohol solvents or ethersolvents are preferable to the others, developers containing estersolvents are far preferred, and developers containing butyl acetate areespecially preferred. From the viewpoint of stripping off the topcoatwith a negative developer, the rate of dissolution of the topcoat in anegative developer is preferably from 1 nm/sec to 300 nm/sec, farpreferably from 10 nm/sec to 100 nm/sec.

The expression of “rate of dissolution of the topcoat in a negativedeveloper” used herein refers to the rate of decrease in thickness ofthe topcoat during exposure to the developer after formation of thetopcoat, which is represented by the rate of thickness decrease duringthe immersion of the topcoat in a 23° C. butyl acetate solution.

When the rate of dissolution of the topcoat in a negative developer isadjusted to 1 nm/sec or above, preferably 10 nm/sec or above, the effectof reducing development defects occurring after development of theresist is produced. On the other hand, adjustment of the foregoing rateto 300 nm/sec or below, preferably 100 nm/sec or below, produces theeffect of improving line edge roughness of patterns of the developedresist, probably under the influence of reduction in unevenness ofexposure during the immersion exposure.

The topcoat may be removed by use of another known developer, e.g., anaqueous alkali solution. An example of an aqueous alkali solution usablefor the removal is an aqueous solution of tetramethylammonium hydroxide.

In the process (c) for exposure via an immersion medium, the exposure ofresist film to light can be carried out in accordance with a generallywell-known method. And it is appropriate that irradiation of the resistfilm with an actinic ray or radiation passing through a given mask beperformed via an immersion liquid. The setting of an exposure amount,though can be made as appropriate, is generally from 1 to 100 mJ/cm².

The wavelengths of a light source usable in exposure apparatus are notparticularly limited in the invention, but it is preferred that thewavelengths of light emitted from a light source used be 250 nm orbelow. Examples of such light include KrF excimer laser light (248 nm),ArF excimer laser light (193 nm), F2 excimer laser light (157 nm), EUVlight (13.5 nm) and electron beams. Among them, ArF excimer laser light(193 nm) is used to greater advantage.

When the immersion exposure is carried out, a process of cleaning thefilm surface with an aqueous chemical may be carried out (1) after filmformation on the substrate and before the exposure process, and/or (2)after the process of exposing the film to light via an immersion liquidand before the process of heating the film.

The suitable liquid as an immersion liquid is a liquid that istransparent at the wavelength of exposure light and has the smallestpossible temperature coefficient of reflective index so that distortionof optical images projected onto the film is minimized. In a specialcase where the exposure light source is ArF excimer laser light (193nm), water is preferably used as the immersion liquid in terms ofavailability and ease of handling in addition to the foregoingviewpoints.

When water is used, an additive (liquid) capable of reducing the surfacetension of water and enhancing surface activity may be added in a slightamount. Such an additive is preferably a liquid in which the resistlayer on a wafer has no solubility, and besides, which has negligibleinfluence on an optical coat provided on the under side of lens element.As water used, distilled water is suitable. Alternatively, pure waterobtained by further filtering the distilled water through an ionexchange filter or the like may be used. The use of such water allowsprevention of distortion caused in optical images projected onto theresist by contamination with impurities.

In the sense that further rise in refractive index is possible, a mediumhaving a refractive index of 1.5 or above can also be used. Such amedium may be a water solution or an organic solvent.

In the present method of pattern formation, the exposure process may becarried out two or more times. In this case, two or more exposures maybe performed by means of the same light source or different lightsources. The first exposure is preferably performed using ArF excimerlaser light (193 nm).

After performing the exposure process, it is preferable to carry out (f)a heating process (referred to as bake or PEB too), and then developmentand rinse are carried out. By these processes, patterns of good qualitycan be obtained. The PEB temperature has no particular limitations solong as resist patterns of good quality are formed, and it is generallywithin the range of 40° C. to 160° C.

In the invention, (d) development is carried out using a negativedeveloper, and thereby a resist pattern is formed. It is preferred thatthe process (d) in which development is carried out using a negativedeveloper be a process of removing soluble portions of the resist filmand the topcoat at the same time.

When the negative development is carried out, an organic developercontaining an organic solvent is preferably used.

The organic developer usable in carrying out negative development is apolar solvent, such as a ketone solvent, an ester solvent, an alcoholsolvent, an amide solvent or an ether solvent, or a hydrocarbon solvent.Examples of a ketone solvent usable therein include 1-octanone,2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, methyl amylketone (IUPAC name: 2-heptanone), 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethylketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone,diacetonyl alcohol, acetyl carbinol, acetophenone, methyl naphthylketone, isophorone and propylene carbonate; and examples of an estersolvent usable therein include methyl acetate, butyl acetate, ethylacetate, isopropyl acetate, amyl acetate, propylene glycol monomethylether acetate, ethylene glycol monoethyl ether acetate, diethyleneglycol monobutyl ether acetate, diethylene glycol monoethyl etheracetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, methyl formate, ethyl formate, butylformate, propyl formate, ethyl lactate, butyl lactate and propyllactate.

Examples of an alcohol solvent usable therein include alcohol compounds,such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropylalcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol,isobutyl alcohol, n-hexyl alcohol, n-heptyl alcohol, n-octyl alcohol andn-decanol; glycol solvents, such as ethylene glycol, diethylene glycoland triethylene glycol; and glycol ether solvents, such as ethyleneglycol monomethyl ether, propylene glycol monomethyl ether, ethyleneglycol monoethyl ether, propylene glycol monoethyl ether, diethyleneglycol monomethyl ether, triethylene glycol monoethyl ether andmethoxymethyl butanol.

Examples of an ether solvent usable therein include dioxane andtetrahydrofuran in addition to the glycol ether solvents as recitedabove.

Examples of an amide solvent usable therein includeN-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide,hexamethylphosphoric triamide and 1,3-dimethyl-2-imidazolidinone.

Examples of a hydrocarbon solvent usable therein include aromatichydrocarbon solvents, such as toluene and xylene, and aliphatichydrocarbon solvents, such as pentane, hexane, octane and decane.

The solvents as recited above may be used as mixtures of two or morethereof, or as mixtures with other solvents or water.

As to the development methods, there are a method of developing bymounding a developer on a substrate surface by surface tension andleaving the developer at rest for a fixed period of time (puddlemethod), a method of spraying a developer on a substrate surface (spraymethod) and a method of keeping on dispensing a developer onto asubstrate spinning at a constant speed while scanning the substrate at aconstant speed with a developer dispense nozzle (dynamic dispensemethod).

The vapor pressure of a negative developer at 20° C. is preferably 5 kPaor below, far preferably 3 kPa or below, particularly preferably 2 kPaor below. By adjusting the vapor pressure of a negative developer to 5kPa or below, evaporation of the developer on the substrate or inside adevelopment cup can be controlled, and thereby in-plane temperatureuniformity of a wafer is improved to result in improvement of in-planedimensional uniformity of a wafer.

Examples of a negative developer having a vapor pressure of 5 kPa orbelow at 20° C. include ketone solvents, such as 1-octanone, 2-octanone,1-nonanone, 2-nonanone, 4-heptanone, methyl amyl ketone (IUPAC name:2-heptanone), 2-hexanone, diisobutyl ketone, cyclohexanone,methylcyclohexanone, phenylacetone and methyl isobutyl ketone; estersolvents, such as butyl acetate, amyl acetate, propylene glycolmonomethyl ether acetate, ethylene glycol monoethyl ether acetate,diethylene glycol monobutyl ether acetate, diethylene glycol monoethylether acetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, butyl formate, propyl formate, ethyllactate, butyl lactate and propyl lactate; alcohol solvents, such asn-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,tert-butyl alcohol, isobutyl alcohol, n-hexyl alcohol, n-heptyl alcohol,n-octyl alcohol and n-decanol; glycol solvents, such as ethylene glycol,diethylene glycol and triethylene glycol; and glycol ether solvents,such as ethylene glycol monomethyl ether, propylene glycol monomethylether, ethylene glycol monoethyl ether, propylene glycol monoethylether, diethylene glycol monomethyl ether, triethylene glycol monoethylether and methoxymethyl butanol; ether solvents, such astetrahydrofuran; amide solvents, such as N-methyl-2-pyrrolidone,N,N-dimethylacetamide and N,N-dimethylformamide; aromatic hydrocarbonsolvents, such as toluene and xylene; and aliphatic hydrocarbonsolvents, such as octane and decane.

Examples of a negative developer which has its vapor pressure in theespecially preferable range of 2 kPa or below at 20° C. include ketonesolvents, such as 1-octanone, 2-octanone, 1-nonanone, 2-nonanone,4-heptanone, methyl amyl ketone (IUPAC name: 2-heptanone), 2-hexanone,diisobutyl ketone, cyclohexanone, methylcyclohexanone and phenylacetone;ester solvents, such as butyl acetate, amyl acetate, propylene glycolmonomethyl ether acetate, ethylene glycol monoethyl ether acetate,diethylene glycol monobutyl ether acetate, diethylene glycol monoethylether acetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate,3-methyl-3-methoxybutyl acetate, ethyl lactate, butyl lactate and propyllactate; alcohol solvents, such as n-butyl alcohol, sec-butyl alcohol,tert-butyl alcohol, isobutyl alcohol, n-hexyl alcohol, n-heptyl alcohol,n-octyl alcohol and n-decanol; glycol solvents, such as ethylene glycol,diethylene glycol and triethylene glycol; and glycol ether solvents,such as ethylene glycol monomethyl ether, propylene glycol monomethylether, ethylene glycol monoethyl ether, propylene glycol monoethylether, diethylene glycol monomethyl ether, triethylene glycol monoethylether and methoxymethyl butanol; amide solvents, such asN-methyl-2-pyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide;aromatic hydrocarbon solvents, such as xylene; and aliphatic hydrocarbonsolvents, such as octane and decane.

To a developer which can be used when negative development is carriedout, a surfactant can be added in an appropriate amount, if needed.

The developer has no particular restriction as to the surfactant addedthereto, so addition of, e.g., an ionic or nonionic surfactantcontaining at least one fluorine atom and/or at least one silicon atommay be made. Examples of such an ionic or nonionic surfactant includethe surfactants disclosed in JP-A-62-36663, JP-A-61-226746,JP-A-61-226745, JP-A-62-170950, JP-A-63-34540, JP-A-7-230165,JP-A-8-62834, JP-A-9-54432, JP-A-9-5988, and U.S. Pat. Nos. 5,405,720,5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511 and5,824,451. Of these surfactants, nonionic surfactants are preferable tothe others. Though no particular restrictions are imposed on suchnonionic surfactants, it is far preferable to use a surfactantcontaining at least one fluorine atom or a surfactant containing atleast one silicon atom.

The amount of a surfactant used is generally from 0.001 to 5 mass %,preferably from 0.005 to 2 mass %, far preferably from 0.01 to 0.5 mass%, of the total amount of the developer to which the surfactant isadded.

Examples of a development method applicable herein include a method ofdipping a substrate for a predetermined period of time into a tankfilled with a developer (dip method), a method of developing by moundinga developer on a substrate surface by surface tension and leaving thedeveloper at rest for a fixed period of time (puddle method), a methodof spraying a developer on a substrate surface (spray method) and amethod of keeping on dispensing a developer onto a substrate spinning ata constant speed while scanning the substrate at a constant speed with adeveloper dispense nozzle (dynamic dispense method).

After the process of negative development, a process of stopping thedevelopment while replacing the negative developer with another solventmay be carried out.

After the completion of the negative development, the present methodpreferably includes a cleaning process using an organicsolvent-containing rinse liquid for negative development.

The rinse liquid used in the rinse process after negative developmenthas no particular restrictions so long as it does not dissolve resistpatterns, and solutions containing general organic solvents can be used.More specifically, the solution suitably used as the rinse liquid is asolution containing at least one kind of organic solvent chosen fromhydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents,amide solvents or ether solvents. And it is preferable that, afternegative development, the cleaning process is carried out using a rinseliquid containing at least one kind of solvent chosen from ketonesolvents, ester solvents, alcohol solvents or amide solvents. It ispreferable by far that, after negative development, the cleaning processis carried out using a rinse liquid containing an alcohol solvent or anester solvent, and it is especially preferable that, after negativedevelopment, the cleaning process is carried out using a rinse liquidcontaining monohydric alcohol. Herein, the monohydric alcohol used inthe rinse process after the negative development may have any ofstraight-chain, branched or cyclic forms, with examples including1-butanol, 2-butanol, 3-methyl-1-butanol, tert-butyl alcohol,1-pentanol, 2-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 2-hexanol,2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol and 4-octanol.Of these alcohol solvents, 1-hexanol, 2-hexanol, 1-heptanol and3-methyl-1-butanol are preferred over the others.

The ingredients recited above may be used as combinations of two or morethereof, or may be used as mixtures of organic solvents other than theabove-recited ones.

The water content in the rinse liquid is preferably 10 mass % or below,far preferably 5 mass % or below, particularly preferably 3 mass % orbelow. By controlling the water content to 10 mass % or below,satisfactory developing properties can be attained.

The vapor pressure of the rinse liquid used after negative development,as measured at 20° C., is preferably from 0.05 kPa to 5 kPa, farpreferably from 0.1 kPa to 5 kPa, especially preferably from 0.12 kPa to3 kPa. By adjusting the vapor pressure of the rinse liquid to the rangeof 0.05 kPa to 5 kPa, in-plane temperature uniformity of a wafer isenhanced, and besides, wafer swelling caused by penetration of the rinseliquid can be controlled; as a result, in-plane dimensional uniformityof a wafer can be improved.

It is also possible to use the rinse liquid to which a surfactant isadded in an appropriate amount.

In the rinse process, the wafer having undergone the negativedevelopment is subjected to cleaning treatment with the organicsolvent-containing rinse liquid. There is no particular restriction onthe method for the cleaning treatment. For example, a method of keepingon coating a substrate spinning at a constant speed with a rinse liquid(spin coating method), a method of dipping a substrate in a tank filledwith a rinse liquid (dip method) and a method of spraying a rinse liquidonto the substrate surface (spray method) can be applied thereto.However, it is preferred that the cleaning treatment be performed by thespin coating method and then the rinse liquid be eliminated from thesubstrate by spinning the substrate at revs ranging from 2,000 rpm to4,000 rpm.

In the invention, it is preferable that resist patterns are formed byfurther performing (e) development with a positive developer.

As the positive developer, an alkali developer can be used to advantage.Examples of such an alkali developer include alkaline aqueous solutionsof inorganic alkalis such as sodium hydroxide, potassium hydroxide,sodium carbonate, sodium silicate, sodium metasilicate and aqueousammonia, primary amines such as ethylamine and n-propylamine, secondaryamines such as diethylamine and di-n-butylamine, tertiary amines such astriethylamine and methyldiethylamine, alcoholamines such asdimethylethanolamine and triethanolamine, quaternary ammonium salts suchas tetramethylammonium hydroxide and tetraethylammonium hydroxide, andcyclic amines such as pyrrole and piperidine. Of these alkaline aqueoussolutions, an aqueous solution of tetraethylammonium hydroxide ispreferred over the others.

The alkali developers as recited above may also be used after alcoholcompounds and surfactants are further added in appropriate amounts.

The alkali concentration of an alkali developer is generally from 0.01to 20 mass %.

The pH of an alkali developer is generally from 10.0 to 15.0.

The time to perform development with an alkali developer is generallyfrom 10 to 300 seconds.

The alkali concentration (and pH) of an alkali developer and thedevelopment time can be adjusted as appropriate according to patterns tobe formed.

As a rinse liquid used in the rinse process carried out after thepositive development, purified water is used. Alternatively, purifiedwater to which a surfactant is added in an appropriate amount may beused.

Further, it is possible to carry out treatment with a supercriticalfluid after development processing or rinse processing for the purposeof eliminating the developer or the rinse liquid adhering to patterns.

Furthermore, it is possible to carry out heat treatment after thetreatment with a supercritical fluid for the purpose of eliminatingwater remaining in patterns.

Resist compositions for negative development, which are usable in theinvention, are described below.

<Resist Composition for Negative Development>

(A) Resin that can Increase in Polarity by Action of Acid

The resin usable in a resist composition according to the invention andcapable of increasing in the polarity by the action of an acid is aresin having groups capable of decomposing by the action of an acid toproduce alkali-soluble groups (hereinafter referred to as“acid-decomposable groups”) in either its main chain, or side chains, orboth (hereinafter referred to as “an acid-decomposable resin”, “anacid-decomposable Resin (A)” or “a Resin (A)”), and preferably a resinhaving mononuclear or polynuclear alicyclic hydrocarbon structures andcapable of increasing its polarity, increasing its solubility in analkali developer and decreasing its solubility in an organic solvent bythe action of an acid (hereinafter referred to as “an alicyclichydrocarbon-containing acid-decomposable resin”). Reasons for thosechanges are not clear, but as a reason it is likely thought that theresin causes a great change in polarity by undergoing the irradiationwith an actinic ray or radiation to result in enhancement of dissolutioncontrasts in both the case of development with a positive developer(preferably an alkali developer) and the case of development with anegative developer (preferably an organic solvent). Further, it isthought that, because of high hydrophobicity of the resin havingmononuclear or polynuclear aliphatic hydrocarbon structures, thedevelopability enhancement is caused in the case where resist filmregions low in irradiation intensity are developed with a negativedeveloper (preferably an organic solvent).

The present resist composition containing a resin capable of increasingthe polarity by the action of an acid can be used suitably for the caseof irradiation with ArF excimer laser.

The acid-decomposable resin includes a unit having an acid-decomposablegroup.

A group suitable as the group capable of decomposing by the action of anacid (the acid-decomposable group) is a group obtained by substituting agroup capable of splitting off by the action of an acid for a hydrogenatom of an alkali-soluble group.

Examples of alkali-soluble groups include groups respectively having aphenolic hydroxyl group, a carboxylic acid group, a fluorinated alcoholgroup, a sulfonic acid group, a sulfonamido group, a sulfonylimidogroup, an (alkylsulfonyl)(alkylcarbonyl)methylene group, an(alkylsulfonyl) (alkylcarbonyl)imido group, abis(alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imido group, abis(alkylsulfonyl)methylene group, a bis(alkylsulfonyl)imido group, atris(alkylcarbonyl)methylene group and a tris(alkylsulfonyl)methylenegroup.

Of these alkali-soluble groups, a carboxylic acid group, a fluorinatedalcohol group (preferably a hexafluoroisopropanol group) and a sulfonicacid group are preferred over the others.

Examples of a group capable of splitting off by the action of an acidinclude groups of formula —C(R₃₆)(R₃₇)(R₃₈), groups of formula—C(R₃₆)(R₃₇)(OR₃₉), and groups of formula —C(R₀₁)(R₀₂)(OR₃₉).

In these formulae, R₃₆ to R₃₉ each represent an alkyl group, acycloalkyl group, an aryl group, an aralkyl group or an alkenyl groupindependently. R₃₆ and R₃₇ may combine with each other to form a ring.R₀₁ and R₀₂ each represent a hydrogen atom, an alkyl group, a cycloalkylgroup, an aryl group, an aralkyl group or an alkenyl groupindependently.

Examples of a group suitable as an acid decomposable group include cumylester groups, enol ester groups, acetal ester groups and tertiary alkylester groups. Of these groups, tertiary alkyl ester groups are preferredover the others.

The alicyclic hydrocarbon-containing acid-decomposable resin ispreferably a resin having at least one kind of repeating units selectedfrom repeating units having alicyclic hydrocarbon-containing partialstructures represented by any of the following formulae (pI) to (pV) orrepeating units represented by the following formula (II-AB).

In the formulae (pI) to (pV), R₁₁ represents a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group or a sec-butyl group, and Z represents atoms forming acycloalkyl group together with the carbon atom.

R₁₂ to R₁₆ each represent a 1-4C straight-chain or branched alkyl group,or a cycloalkyl group independently, provided that at least one of R₁₂to R₁₄, or either R₁₅ or R₁₆ represents a cycloalkyl group.

R₁₇ to R₂₁ each represent a hydrogen atom, a 1-4C straight-chain orbranched alkyl group or a cycloalkyl group independently, provided thatat least one of R₁₇ to R₂₁ represents a cycloalkyl group. In addition,either R₁₉ or R₂₁ is required to represent a 1-4C straight-chain orbranched alkyl group or a cycloalkyl group.

R₂₂ to R₂₅ each represent a hydrogen atom, a 1-4C straight-chain orbranched alkyl group or a cycloalkyl group independently, provided thatat least one of R₂₂ to R₂₅ represents a cycloalkyl group. Alternatively,R₂₃ and R₂₄ may combine with each other to form a ring.

In the formula (II-AB), R₁₁′ and R₁₂′ each represent a hydrogen atom, acyano group, a halogen atom or an alkyl group independently.

Z′ represents atoms forming an alicyclic structure together with the twobonded carbon atoms (C—C).

The formula (II-AB) is preferably the following formula (II-AB 1) orformula (II-AB2).

In the formulae (II-AB 1) and (II-AB2), R₁₃′ to R₁₆′ each independentlyrepresent a hydrogen atom, a halogen atom, a cyano group, —COOH, —COOR₅,a group capable of decomposing by the action of an acid,—C(═O)—X-A′—R₁₇′, an alkyl group or a cycloalkyl group. At least two ofR₁₃′ to R₁₆′ may combine with each other to form a ring.

Herein, R₅ represents an alkyl group, a cycloalkyl group or a grouphaving a lactone structure.

X represents an oxygen atom, a sulfur atom, —NH—, —NHSO₂— or —NHSO₂NH—.A′ represents a single bond or a divalent linkage group.

R₁₇′ represents —COOH, —COOR₅, —CN, a hydroxyl group, an alkoxyl group,—CO—NH—R₆, —CO—NH—SO₂—R₆ or a group having a lactone structure.

R₆ represents an alkyl group or a cycloalkyl group.

n represents 0 or 1.

The alkyl group which R₁₂ to R₂₅ each can represent in the formulae (pI)to (pV) is preferably a 1-4C straight-chain or branched alkyl group.

The cycloalkyl group which R₁₁ to R₂₅ each can represent or thecycloalkyl group which can be formed of Z and the carbon atom may bemonocyclic or polycyclic. Examples of such a cycloalkyl group includegroups each containing at least 5 carbon atoms and having a monocyclo,bicyclo, tricyclo or tetracyclo structure. The number of carbon atoms insuch a structure is preferably from 6 to 30, particularly preferablyfrom 7 to 25. These cycloalkyl groups may have substituents.

Suitable examples of such a cycloalkyl group include an adamantyl group,a noradamantyl group, a decaline residue, a tricyclodecanyl group, atetracyclododecanyl group, a norbornyl group, a cedrol group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup, a cyclodecanyl group and a cyclododecanyl group. Of these groups,an adamantyl group, a norbornyl group, a cyclohexyl group, a cyclopentylgroup, a tetracyclodecanyl group and a tricyclodecanyl group arepreferred over the others.

Each of those alkyl groups and cycloalkyl groups may further have asubstituent. Examples of such a substituent include an alkyl group(1-4C), a halogen atom, a hydroxyl group, an alkoxyl group (1-4C), acarboxyl group and an alkoxycarbonyl group (2-6C). Herein, the alkyl,alkoxy and alkoxycarbonyl groups each may further have a substituent,such as a hydroxyl group, a halogen atom or an alkoxyl group.

In the resins, the structures represented by the formulae (pI) to (pV)can be used for protection of alkali-soluble groups. Examples of suchalkali-soluble groups include various groups known in this technicalfield.

More specifically, such a protected alkali-soluble group has a structureformed by substituting the structure represented by any of the formulae(pI) to (pV) for the hydrogen atom of a carboxylic acid group, asulfonic acid group, a phenol group or a thiol group. Of thesestructures, structures formed by substituting the structures representedby formulae (pI) to (pV) for the hydrogen atoms of carboxylic acidgroups or sulfonic acid groups are preferable to the others.

As repeating units containing alkali-soluble groups protected by thestructures of formulae (pI) to (pV), repeating units represented by thefollowing formula (pA) are suitable.

In the formula (pA), each R represents a hydrogen atom, a halogen atomor a 1-4C straight-chain or branched alkyl group. Two or more Rs may bethe same or different.

A represents a single bond, an alkylene group, an ether group, athioether group, a carbonyl group, an ester group, an amido group, asulfonamide group, a urethane group, a urea group, or a combination oftwo or more of the groups recited above, preferably a single bond.

Rp₁ represents any of the formulae (pI) to (pV).

The most suitable of repeating units represented by the formula (pA) isa repeating unit derived from 2-alkyl-2-adamantyl (meth)acrylate ordialkyl(1-adamantyl)methyl (meth)acrylate.

Examples of the repeating unit having an acid-decomposable group areillustrated below, but these examples should not be construed aslimiting the scope of the invention.

(In the following formulae, Rx represents H, CH₃ or CH₂OH, and Rxa andRxb each represent a 1-4C alkyl group.)

Examples of a halogen atom which R₁₁′ and R₁₂′ each can represent in theformula (II-AB) include a chlorine atom, a bromine atom, a fluorine atomand an iodine atom.

Examples of an alkyl group which R₁₁′ and R₁₂′ each can represent in theformula (II-AB) include 1-10C straight-chain or branched alkyl groups.

The atoms Z′ for forming an alicyclic structure are atoms forming anunsubstituted or substituted alicyclic hydrocarbon as a repeating unitof the resin, particularly preferably atoms forming a bridged alicyclichydrocarbon as a repeating unit.

Examples of a skeleton of the alicyclic hydrocarbon formed include thesame skeletons as the alicyclic hydrocarbon groups represented by R₁₂ toR₂₅ in the formulae (pI) to (pV) have.

The skeleton of the alicyclic hydrocarbon may have a substituent.Examples of such a substituent include the groups represented by R₁₃′ toR₁₆′ in the formula (II-AB 1) or (II-AB2).

In the alicyclic hydrocarbon-containing acid-decomposable resin relatingto the invention, groups capable of decomposing by the action of an acidcan be incorporated into at least one type of repeating units chosenfrom repeating units having aliphatic hydrocarbon-containing partialstructures represented by any of the formulae (pI) to (pV), repeatingunits represented by the formula (II-AB) or repeating units ofcopolymerization components described hereinafter. However, it ispreferable that the groups capable of decomposing by the action of anacid are incorporated into repeating units having alicyclichydrocarbon-containing partial structures represented by any of theformulae (pI) to (pV).

Various kinds of substituents as R₁₃′ to R₁₆′ in the formula (II-AB1) or(II-AB2) may also become substituents of atoms Z′ for forming analicyclic hydrocarbon structure or a bridged alicyclic hydrocarbonstructure in the formula (II-AB).

Examples of repeating units represented by the formula (II-AB 1) or(II-AB2) are illustrated below, but these examples should not beconstrued as limiting the scope of the invention.

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention preferably has lactone groups. As the lactone groups, anygroups can be used as long as they have lactone structures. Suitableexamples of a lactone group include groups having 5- to 7-membered ringlactone structures, preferably groups in a state that 5- to 7-memberedring lactone structures fuse with other ring structures to form bicycloor spiro structures. It is preferable by far that the alicyclichydrocarbon-containing acid-decomposable resin for use in the inventionhas repeating units containing the groups having lactone structuresrepresented by any of the following formulae (LC1-1) to (LC1-16).Alternatively, the groups having lactone structures may be bondeddirectly to the main chain. The lactone structures used to advantage aregroups represented by the formulae (LC1-1), (LC1-4), (LC1-5), (LC1-6),(LC1-13) and (LC1-14), and the use of specified lactone structurescontributes to improvements in line edge roughness and developmentdefects.

The lactone structure moieties each may have a substituent (Rb₂) orneedn't. Suitable examples of a substituent (Rb₂) include 1-8C alkylgroups, 4-7C cycloalkyl groups, 1-8C alkoxyl groups, 1-8C alkoxycarbonylgroups, a carboxyl group, halogen atoms, a hydroxyl group, a cyano groupand acid-decomposable groups. n2 represents an integer of 0 to 4. Whenn2 is 2 or above, a plurality of Rb2s may be the same or different, orthey may combine with each other to form a ring.

Examples of a repeating unit containing a group having a lactonestructure represented by any of the formulae (LC1-1) to (LC1-16) includethe repeating units represented by the formula (II-AB 1) or (II-AB2)wherein at least one of R₁₃′ to R₁₆′ is a group having the lactonestructure represented by any of the formulae (LC1-1) to (LC1-16) (forinstance, R₅ in —COOR₅ represents a group having the lactone structurerepresented by any of the formulae (LC1-1) to (LC1-16)), and repeatingunits represented by the following formula (AI).

In the formula (AI), Rb₀ represents a hydrogen atom, a halogen atom or a1-4C alkyl group. Examples of a suitable substituent the alkyl group ofRbo may have include a hydroxyl group and halogen atoms.

Examples of a halogen atom represented by Rb₀ include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

Rb₀ is preferably a hydrogen atom, a methyl group, a hydroxymethyl groupor a trifluoromethyl group, and more preferably a hydrogen atom or amethyl group.

Ab represents a single bond, an alkylene group, a divalent linkage grouphaving a mononuclear or polynuclear alicyclic hydrocarbon structure, anether linkage, an ester linkage, a carbonyl group, or a divalent groupformed by combining two or more of the groups recited above. Thepreferred as Ab is a single bond or a linkage group represented by-Ab₁-CO₂—. Ab₁ is a straight-chain or branched alkylene group or amononuclear or polynuclear cycloalkylene group, preferably a methylenegroup, an ethylene group, a cyclohexylene group, an adamantylene groupor a norbornylene group.

V represents a group represented by any of the formulae (LC 1-1) to(LC1-16).

A repeating unit having a lactone structure generally has opticalisomers, and any of the optical isomers may be used. Further, oneoptical isomer may be used by itself, or two or more of optical isomersmay be used as a mixture. When one optical isomer is mainly used, theoptical purity (ee) thereof is preferably 90 or above, far preferably 95or above.

Examples of a repeating unit containing a group having a lactonestructure are illustrated below, but these examples should not beconstrued as limiting the scope of the invention.

(In each of the following formulae, Rx is H, CH₃, CH₂OH or CF₃)

(In each of the following formulae, Rx is H, CH₃, CH₂OH or CF₃)

(In each of the following formulae, Rx is H, CH₃, CH₂OH or CF₃)

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention preferably has repeating units containing organic groupshaving polar groups, especially repeating units having alicyclichydrocarbon structures substituted with polar groups. By having suchrepeating units, the resin can contribute to enhancement of adhesivenessto a substrate and affinity for a developer. As the alicyclichydrocarbon part of the alicyclic hydrocarbon structure substituted witha polar group, an adamantyl group, a diamantyl group or a norbornylgroup is suitable. As the polar group in such a structure, a hydroxylgroup or a cyano group is suitable. As the alicyclic hydrocarbonstructures substituted with polar groups, partial structures representedby the following formulae (VIIa) to (VIId) are suitable.

In the formulae (VIIa) to (VIII), R_(2C) to R_(4C) each represent ahydrogen atom, a hydroxyl group or a cyano group independently, providedthat at least one of them represents a hydroxyl group or a cyan group.In such partial structures, it is preferable that one of R_(2C) toR_(4C) is a hydroxyl group and the remainder are hydrogen atoms, andthat two of R_(2C) to R_(4C) are hydroxyl groups and the remainder is ahydrogen atom.

In the partial structure of formula (VIIa), the case where two of R_(2C)to R_(4C) are hydroxyl groups and the remainder is a hydrogen atom isfar preferred.

Examples of repeating units containing groups represented by theformulae (VIIa) to (VIId) include the repeating units represented by theformula (II-AB1) or (II-AB2) wherein at least one of R₁₃′ to R₁₆′ is agroup represented by any of the formulae (VIIa) to (VIId) (for example,R₅ in —COOR₅ represents a group represented by any of the formulae(VIIa) to (VIId)), and repeating units represented by the followingformulae (AIIa) to (AIId).

In the formula (AIIa) to (AIId), R_(1C) represents a hydrogen atom, amethyl group, a trifluoromethyl group or a hydroxymethyl group, andR_(2C) to R4C have the same meanings as in the formulae (VIIa) to(VIII).

Examples of repeating units represented by the formulae (AIIa) to (AIId)are illustrated below, but these examples should not be construed aslimiting the scope of the invention.

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention may have repeating units represented by the followingformula (VIII).

In the formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents ahydrogen atom, a hydroxyl group, an alkyl group or —OSO₂—R₄₂. R₄₂represents an alkyl group, a cycloalkyl group or a camphor residue. Thealkyl groups of R₄₁ and R₄₂ may be substituted with halogen atoms(preferably fluorine atoms) or so on.

Examples of a repeating unit represented by the formula (VIII) areillustrated below, but these examples should not be construed aslimiting the scope of the invention.

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention preferably has repeating units containing alkali-solublegroups, and far preferably has repeating units containing carboxylgroups. The presence of such groups in the repeating units can enhanceresolution in the use for contact hole. Suitable examples of a repeatingunit containing a carboxyl group include a repeating unit containing thecarboxyl group bonded directly to the main chain of resin, such as arepeating unit derived from acrylic acid or methacrylic acid, arepeating unit containing the carboxyl group attached to the main chainof resin via a linkage group, and a unit introduced as a polymer chainterminal by using a polymerization initiator or chain transfer agenthaving an alkali-soluble group at the time of polymerization. Therein,the linkage group may have a mononuclear or polynuclear cyclichydrocarbon structure. Of these repeating units, those derived fromacrylic acid and methacrylic acid in particular are preferred.

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention may further have repeating units which each contain 1 to 3groups represented by the following formula (F1). The presence of thesegroups contributes to improvement in line edge roughness quality.

In the formula (F1), R₅₀ to R₅₅ each represent a hydrogen atom, afluorine atom or an alkyl group independently, provided that at leastone of R₅₀ to R₅₅ is a fluorine atom or an alkyl group at least onehydrogen atom of which is substituted with a fluorine atom.

Rx represent a hydrogen atom or an organic group (preferably anacid-decomposable blocking group, an alkyl group, a cycloalkyl group, anacyl group or an alkoxycarbonyl group).

The alkyl group represented by R₅₀ to R₅₅ each may be substituted with ahalogen atom such as a fluorine atom, a cyano group or so on, andsuitable examples thereof include 1-3C alkyl groups, such as a methylgroup and a trifluoromethyl group.

Nevertheless, it is preferable that all of R₅₀ to R₅₅ are fluorineatoms.

Suitable examples of an organic group represented by Rx includeacid-decomposable blocking groups, and alkyl, cycloalkyl, acyl,alkylcarbonyl, alkoxycarbonyl, alkoxycarbonylmethyl, alkoxymethyl and1-alkoxyethyl groups which each may have a substituent.

The repeating units containing groups represented by the formula (F1)are preferably repeating units represented by the following formula(F2).

In the formula (F2), Rx represents a hydrogen atom, a halogen atom, or a1-4C alkyl group. The substituent the alkyl group of Rx may have ispreferably a hydroxyl group or a halogen atom.

Fa represents a single bond, or a straight-chain or branched alkylenegroup (preferably a single bond).

Fb represents a mononuclear or polynuclear cyclic hydrocarbon group.

Fc represents a single bond, or a straight-chain or branched alkylenegroup (preferably a single bond or a methylene group).

F1 represents a group represented by the formula (F1).

P1 represents 1, 2 or 3.

The cyclic hydrocarbon group of Fb is preferably a cyclopentylene group,a cyclohexylene group or a norbornylene group.

Examples of the repeating unit having a group represented by the formula(F1) are illustrated below, but these examples should not be construedas limiting the scope of the invention.

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention may further contain repeating units having alicyclichydrocarbon structures and not showing acid decomposability. By thepresence of such repeating units, elution of low molecular componentsfrom a resist coating into an immersion liquid during the performance ofimmersion lithography can be reduced. Examples of such repeating unitsinclude those derived from 1-adamantyl (meth)acrylate, tricyclodecanyl(meth)acrylate and cyclohexayl (meth)acrylate.

Examples of the repeating units having alicyclic hydrocarbon structuresand not showing acid decomposability include repeating units containingneither a hydroxyl group nor a cyano group, and are preferably repeatingunits represented by the following formula (IX).

In the formula (IX), R₅ represents a hydrocarbon group having at leastone cyclic structure and containing neither a hydroxyl group nor a cyanogroup.

Ra represents a hydrogen atom, an alkyl group or —CH₂—O—Ra₂. Herein, Ra₂represents a hydrogen atom, an alkyl group or an acyl group. Ra ispreferably a hydrogen atom, a methyl group, a hydroxymethyl group or atrifluoromethyl group, and more preferably a hydrogen atom or a methylgroup.

The cyclic structure contained in R₅ may be a monocyclic hydrocarbongroup or a polycyclic hydrocarbon group. Examples of the monocyclichydrocarbon group include 3-12C cycloalkyl groups such as a cyclopentylgroup, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group,and 3-12C cycloalkenyl groups such as a cyclohexenyl group. Of thesemonocyclic hydrocarbon groups, 3-7C monocyclic hydrocarbon groups,especially a cyclopentyl group and a cyclohexyl group, are preferredover the others.

The polycyclic hydrocarbon group may be an assembled-ring hydrocarbongroup or a bridged-ring hydrocarbon group. Examples of theassembled-ring hydrocarbon group include a bicyclohexyl group and aperhydronaphthalenyl group. Examples of the bridged hydrocarbon ringinclude bicyclic hydrocarbon rings such as a pinane ring, a bornanering, a norpinane ring, a norbornane ring and bicyclooctane rings (e.g.,a bicyclo[2.2.2]octane ring, a bicyclo[3.2.1]octane ring), tricyclichydrocarbon rings such as a homobredane ring, an adamantane ring, atricyclo[5.2.1.02°6]decane ring and a tricyclo[4.3.1.12°5]undecane ring,and tetracyclic hydrocarbon rings such as atetracyclo[4.4.0.12°51′1°]dodecane ring and aperhydro-1,4-methano-5,8-methanonaphthalene ring. And additionalexamples of the bridged hydrocarbon ring include condensed hydrocarbonrings formed by fusing together two or more of 5- to 8-memberedcycloalkane rings such as perhydronaphthalene (decaline),perhydroanthracene, perhydrophenanthrene, perhydroacenaphthene,perhydrofluorene, perhydroindene and perhydrophenalene rings.

Examples of a bridged-ring hydrocarbon group suitable as the cyclicstructure of R₅ include a norbornyl group, an adamantyl group, abicyclooctanyl group and a tricyclo[5.2.1.02°6]decanyl group. Of thesegroups, a norbornyl group and an adamantyl group are preferred over theothers.

Each of the alicyclic hydrocarbon groups recited above may have asubstituent. Examples of a substituent suitable for those groups eachinclude a halogen atom, an alkyl group, a hydroxyl group protected by aprotective group, and an amino group protected by a protective group.Suitable examples of the halogen atom include bromine, chlorine andfluorine atoms. Suitable examples of the alkyl group include methyl,ethyl, butyl and t-butyl groups. These alkyl groups each may furtherhave a substituent. Examples of the substituent include a halogen atom,an alkyl group, a hydroxyl group protected by a protective group and anamino group protected by a protective group.

Examples of such protective groups include an alkyl group, a cycloalkylgroup, an aralkyl group, a substituted methyl group, a substituted ethylgroup, an acyl group, an alkoxycarbonyl group and an aralkyloxycarbonylgroup. Suitable examples of the alkyl group include 1-4C alkyl groups,those of the substituted methyl group include methoxymethyl,methoxythiomethyl, benzyloxymethyl, t-butoxymethyl and2-methoxyethoxymethyl groups, those of the substituted ethyl groupinclude 1-ethoxyethyl and 1-methyl-1-methoxyethyl groups, those of theacyl group include 1-6C aliphatic acyl groups such as formyl, acetyl,propionyl, butyryl, isobutyryl, valeryl and pivaloyl groups, and thoseof the alkoxycarbonyl group include 1-4C alkoxycarbonyl groups.

The proportion of repeating units represented by the formula (IX), whichhave neither a hydroxyl group nor a cyano group is preferably from 0 to40 mole %, far preferably from 0 to 20 mole %, with respect to the totalrepeating units of the alicyclic hydrocarbon-containingacid-decomposable resin.

Examples of a repeating unit represented by the formula (IX) areillustrated below, but these examples should not be construed aslimiting the scope of the invention.

In the following structural formulae, Ra represents H, CH₃, CH₂OH orCF₃.

In addition to the repeating structural units recited above, thealicyclic hydrocarbon-containing acid-decomposable resin for use in theinvention can contain a wide variety of repeating structural units forthe purpose of controlling dry etching resistance, suitability forstandard developers, adhesiveness to substrates, resist profile, andbesides, characteristics generally required for resist, such asresolution, heat resistance and sensitivity.

Examples of such repeating structural units include repeating structuralunits corresponding to the monomers as recited below, but these examplesshould not be construed as limiting the scope of the invention.

By having those repeating units, it becomes possible to make fineadjustments to properties required for the alicyclichydrocarbon-containing acid-decomposable resin, especially propertiesincluding:

(1) solubility in a coating solvent,

(2) film formability (glass transition temperature),

(3) solubility in a positive developer and solubility in a negativedeveloper,

(4) thinning of film (hydrophilic-hydrophobic balance, alkali-solublegroup selection),

(5) adhesion of unexposed areas to a substrate, and

(6) dry etching resistance.

Examples of monomers suitable for the foregoing purposes includecompounds which each have one addition-polymerizable unsaturated bondand are selected from acrylic acid esters, methacrylic acid esters,acrylamides, methacrylamides, allyl compounds, vinyl ethers, or vinylesters.

In addition to those monomers, any other monomers may be copolymerizedso long as they are addition-polymerizable unsaturated compounds capableof forming copolymers together with monomers corresponding to thevarious repeating structural units mentioned above.

The ratio between mole contents of repeating structural units in thealicyclic hydrocarbon-containing acid-decomposable resin can be chosenappropriately for adjusting dry etching resistance, standard developersuitability, adhesion to substrates, resist profile, and characteristicsgenerally required for resist, such as resolution, heat resistance andsensitivity.

Examples of a preferred state of the alicyclic hydrocarbon-containingacid-decomposable resin for use in the invention include the following.

(1) A state of containing repeating units each having an alicyclichydrocarbon-containing partial structure represented by any of theformulae (pI) to (pV) (side-chain type).

Herein, the rep eating units contained are preferably (meth)acrylaterepeating units each having a structure containing any of (pI) to (pV).

(2) A state of containing repeating units represented by the formula(II-AB) (main-chain type). However, the state (2) further includes thefollowing.

(3) A state of having repeating units represented by the formula(II-AB), maleic anhydride derivative and (meth)acrylate structures(hybrid type).

The content of repeating units having acid-decomposable groups in thealicyclic hydrocarbon-containing acid-decomposable resin is preferablyfrom 10 to 60 mole %, far preferably from 20 to 50 mole %, furtherpreferably from 25 to 40 mole %, of the total repeating structuralunits.

The content of repeating units having acid-decomposable groups in anacid-decomposable resin is preferably from 10 to 60 mole %, farpreferably from 20 to 50 mole %, further preferably from 25 to 40 mole%, of the total repeating structural units.

The content of repeating units having alicyclic hydrocarbon-containingpartial structures represented by the formulae (pI) to (pV) in thealicyclic hydrocarbon-containing acid-decomposable resin is preferablyfrom 20 to 70 mole %, far preferably from 20 to 50 mole %, furtherpreferably from 25 to 40 mole %, of the total repeating structuralunits.

The content of repeating units represented by the formula (II-AB) in thealicyclic hydrocarbon-containing acid-decomposable resin is preferablyfrom 10 to 60 mole %, far preferably from 15 to 55 mole %, furtherpreferably from 20 to 50 mole %, of the total repeating structuralunits.

The content of repeating units having lactone rings in anacid-decomposable resin is preferably from 10 to 70 mole %, farpreferably from 20 to 60 mole %, further preferably from 25 to 40 mole%, of the total repeating structural units.

The content of repeating units containing organic groups having polargroups in an acid-decomposable resin is preferably from 1 to 40 mole %,far preferably from 5 to 30 mole %, further preferably from 5 to 20 mole%, of the total repeating structural units.

In the resin for use in the invention, the content of repeatingstructural units based on monomers as additional copolymerizingcomponents can also be chosen appropriately according to the intendedresist performance. In general, the proportion of such repeatingstructural units is preferably 99 mole % or below, far preferably 90mole % or below, further preferably 80 mole % or below, based on thetotal mole number of the repeating structural units having alicyclichydrocarbon-containing partial structures represented by the formulae(pI) to (pV) and the repeating units represented by the formula (II-AB).

When the present resist composition for negative development is designedfor ArF exposure use, it is advantageous for the resin used therein tohave no aromatic group in point of transparency to ArF light.

As to the alicyclic hydrocarbon-containing acid-decomposable resin foruse in the invention, it is preferable that (meth)acrylate repeatingunits constitute all the repeating units of the resin. Herein, all therepeating units may be either acrylate repeating units, or methacrylaterepeating units, or mixed acrylate-and-methacrylate repeating units.However, it is preferable that the acrylate repeating units is at most50 mole % of the total repeating units.

The alicyclic hydrocarbon-containing acid-decomposable resin ispreferably a copolymer having (meth)acrylate repeating units of threetypes: a type of having at least a lactone ring, a type of having anorganic group substituted with at least either hydroxyl or cyano group,and a type of having an acid-decomposable group.

The alicyclic hydrocarbon-containing acid-decomposable resin is farpreferably a ternary copolymer containing 20-50 mole % of repeatingunits having alicyclic hydrocarbon-containing partial structuresrepresented by any of the formulae (pI) to (pV), 20-50 mole % ofrepeating units having lactone structures and 5-30 mole % of repeatingunits having alicyclic hydrocarbon structures substituted with polargroups, or a quaternary copolymer further containing 0-20 mole % ofother repeating units.

The resin preferred in particular is a ternary copolymer containing20-50 mole % of repeating units containing acid-decomposable groups,which are represented by any of the following formulae (ARA-1) to(ARA-7), 20-50 mole % of repeating units containing lactone groups,which are represented by any of the following formulae (ARL-1) to(ARL-7), and 5-30 mole % of repeating units having alicyclic hydrocarbonstructures substituted with polar groups, which are represented by anyof the following formulae (ARH-1) to (ARH-3), or a quaternary copolymerfurther containing 5-20 mole % of repeating units having carboxyl groupsor structures represented by the formula (F1), or repeating units havingalicyclic hydrocarbon structures but not showing acid decomposability.

In the following formulae, R_(xy1) represents a hydrogen atom or amethyl group, R_(xa1) and R_(xb1) each represent a methyl group or anethyl group independently, and Rxe1 represents a hydrogen atom or amethyl group.

In the following formulae, R_(xy1) represents a hydrogen atom or amethyl group, R_(xd1) represents a hydrogen atom or a methyl group, andR_(xe1) represents a trifluoromethyl group, a hydroxyl group or a cyanogroup.

In the following formulae, R_(xy1) represents a hydrogen atom or amethyl group.

The alicyclic hydrocarbon-containing acid-decomposable resin for use inthe invention can be synthesized according to general methods (e.g.,radical polymerization). As examples of a general synthesis method,there are known a batch polymerization method in which polymerization iscarried out by dissolving monomer species and an initiator in a solventand heating them, and a drop polymerization method in which a solutioncontaining monomer species and an initiator is added dropwise to aheated solvent over 1 to 10 hours. However, it is preferred that thedrop polymerization method be used. Examples of a solvent usable in thepolymerization reaction include ethers, such as tetrahydrofuran,1,4-dioxane and diisopropyl ether; ketones, such as methyl ethyl ketoneand methyl isobutyl ketone; ester solvents, such as ethyl acetate; amidesolvents, such as dimethylformamide and dimethylacetamide; and solventsdescribed hereafter which can dissolve the present composition, such aspropylene glycol monomethyl ether acetate, propylene glycol monomethylether and cyclohexanone. It is preferable that the polymerization iscarried out using the same solvent as used for the present resistcomposition. By doing so, it becomes possible to prevent particles fromdeveloping during storage.

The polymerization reaction is preferably carried out in an atmosphereof inert gas, such as nitrogen or argon. And the polymerization isinitiated using a commercially available radical initiator (e.g., anazo-type initiator or peroxide) as polymerization initiator. The radicalinitiator is preferably an azo-type initiator, and more specifically, anazo-type initiator having an ester group, a cyano group or a carboxylgroup.

Examples of such a preferred azo-type initiator includeazobisisobutyronitrile, azobisdimethylvaleronitrile and dimethyl2,2′-azobis(2-methylpropionate). An addition of such an initiator may bemade in the course of polymerization or such an initiator may be addedin several portions, if desired. After the conclusion of the reaction,the reaction solution is poured into a solvent, and the intended polymeris collected as a powder or a solid. The concentration of reactingspecies is from 5 to 50 mass %, preferably from 10 to 30 mass %, and thereaction temperature is generally from 10° C. to 150° C., preferablyfrom 30° C. to 120° C., far preferably from 60° C. to 100° C.

The polymer thus synthesized can be purified by the same method asapplicable in the case of Resin (X) described hereinafter. For thepurification, a usual method is applicable, and examples thereof includea liquid-liquid extraction method in which residual monomers andoligomeric components are eliminated by washing with water or bycombined use of appropriate solvents, a method of performingpurification in a solution state, such as an ultrafiltration method inwhich only components of molecular weight lower than a specific valueare extracted and eliminated, a reprecipitation method in which a resinsolution is dripped into a poor solvent to result in coagulation of theresin and elimination of residual monomers and so on, and a method ofperforming purification in a solid state, such as a method of washingfiltered resin slurry with a poor solvent.

As to the resin relating to the invention, the weight average molecularweight thereof is preferably from 1,000 to 200,000, far preferably from1,000 to 20,000, particularly preferably from 1,000 to 15,000, asmeasured by GPC and calculated in terms of polystyrene. By adjusting theweight average molecular weight to fall within the range of 1,000 to200,000, declines in heat resistance and dry etching resistance can beprevented, and besides, degradation in developability and filmformability deterioration from an increased viscosity can be prevented.

The polydispersity (molecular weight distribution) of the resin used isgenerally from 1 to 5, preferably from 1 to 3, far preferably from 1.2to 3.0, particularly preferably from 1.2 to 2.0. When the polydispersityis smaller, the resist pattern formed is the more excellent inresolution and resist profile, and besides, it has the smoother sidewall and the better roughness quality.

The total amount of resins relating to the invention, which are mixed inthe present resist composition, is from 50 to 99.9 mass %, preferablyfrom 60 to 99.0 mass %, of the total solids in the resist composition.

In the invention, one kind of resin may be used, or two or more kinds ofresins may be used in combination.

From the viewpoint of compatibility with a protective film composition,it is appropriate that the present alicyclic hydrocarbon-containingacid-decomposable resin, preferably the present resist composition,contain neither fluorine atom nor silicon atom.

(B) Compound Capable of Generating Acid upon Irradiation with ActinicRay or Radiation

The resist composition according to the invention contains a compoundcapable of generating an acid upon irradiation with an actinic ray orradiation (which is also referred to as “a photo-acid generator” or“Component (B)”).

The compound usable as such a photo-acid generator can be selectedappropriately from photo-initiators for cationic photopolymerization,photo-initiators for radical photopolymerization, photodecoloring agentsfor dyes, photodiscoloring agents, compounds used in microresists andknown to generate acids upon irradiation with an actinic ray orradiation, or mixtures of two or more thereof.

Examples of such compounds include diazonium salts, phosphonium salts,sulfonium salts, iodonium salts, imide sulfonate, oxime sulfonate,diazodisulfone, disulfone and o-nitrobenzylsulfonate.

In addition, polymeric compounds having such groups or compounds as togenerate acids upon exposure to an actinic ray or radiation in a stateof being introduced in their main or side chains can also be used.Examples of those polymeric compounds include the compounds as disclosedin U.S. Pat. No. 3,849,137, German Patent No. 3914407, JP-A-63-26653,JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452,JP-A-62-153853 and JP-A-63-146029.

Further, the compounds capable of generating acids by the action oflight as disclosed in U.S. Pat. No. 3,779,778 and European Patent No.126,712 can be used too.

Of the compounds capable of decomposing upon irradiation with an actinicray or radiation to generate acids, compounds represented by thefollowing formulae (ZI), (ZII) and (ZIII) respectively are preferable.

In the formula (ZI), R₂₀₁, R₂₀₂ and R₂₀₃ each represent an organic groupindependently.

X″ represents a non-nucleophilic anion, preferably a sulfonic acidanion, a carboxylic acid anion, a bis(alkylsulfonyl)amide anion, atris(alkylsulfonyl)methide anion, BF₄, PF₆ or SbF₆, far preferably acarbon-containing organic anion.

Examples of an organic anion preferred as X-include organic anionsrepresented by the following formulae.

In the above formulae, Rc₁ represents an organic group.

Examples of the organic group as Rc₁ include groups containing 1 to 30carbon atoms, preferably alkyl groups and aryl groups, which each may besubstituted, and groups formed by connecting two or more of those groupsvia one or more of linkage groups, such as a single bond, —O—, —CO₂—,—S—, —SO₃— and —SO₂N(Rd₁)-. Rd₁ represents a hydrogen atom or an alkylgroup.

Rc₃, Rc₄ and Rc₅ each represent an organic group independently. Examplesof organic groups preferred as Rc₃, Rc₄ and Rc₅ include the same organicgroups as the preferred of Rc₁, especially 1-4C perfluoroalkyl groups.

Rc₃ and Rc₄ may combine with each other to form a ring. The group formedby combining Rc₃ with Rc₄ is an alkylene group or an arylene group,preferably a 2-4C perfluoroalkylene group.

The organic groups particularly preferred as Rc₁, Rc₃, Rc₄ and Rc₅ eachare alkyl groups substituted with fluorine atoms or fluoroalkyl groupsat their respective 1-positions and phenyl groups substituted withfluorine atoms or fluoroalkyl groups. By containing a fluorine atom or afluoroalkyl group, the acid generated by irradiation with light can havehigh acidity to result in enhancement of the sensitivity. Likewise, thering formation by combination of Rc₃ and Rc₄ allows an acidity increaseof the acid generated by irradiation with light to result in enhancementof the sensitivity.

The number of carbon atoms in the organic group as R₂₀₁, R₂₀₂ and R₂₀₃each is generally from 1 to 30, preferably from 1 to 20.

Two of R₂₀₁ to R₂₀₃ may combine with each other to form a ringstructure, and the ring formed may contain an oxygen atom, a sulfuratom, an ester linkage, an amide linkage or a carbonyl group. Examplesof a group formed by combining two of R₂₀₁, R₂₀₂ and R₂₀₃ includealkylene groups (such as a butylene group and a pentylene group).

Examples of organic groups as R₂₀₁, R₂₀₂ and R₂₀₃ include theircorresponding groups in compounds (ZI-1), (ZI-2) and (ZI-3) illustratedbelow.

Additionally, the photo-acid generator may be a compound having two ormore of structures represented by formula (ZI). For instance, thephoto-acid generator may be a compound having a structure that at leastone of R₂₀₁, R₂₀₂ and R₂₀₃ in one compound represented by formula (ZI)is united with at least one of R₂₀₁, R₂₀₂ and R₂₀₃ in another compoundrepresented by formula (ZI).

Far preferred examples of a compound (ZI) include compounds (ZI-1),(ZI-2) and (ZI-3) explained blow.

The compound (ZI-1) is an arylsulfonium compound represented by theformula (ZI) wherein at least one of R₂₀₁ to R₂₀₃ is an aryl group,namely a compound having an arylsulfonium as its cation.

In such an arylsulfonium compound, all of R₂₀₁ to R₂₀₃ may be arylgroups, or one or two of R₂₀₁ to R₂₀₃ may be aryl groups and theremainder may be an alkyl group or a cycloalkyl group.

Examples of such an arylsulfonium compound include a triarylsulfoniumcompound, a diarylalkylsulfonium compound, an aryldialkylsulfoniumcompound, a diarylcycloalkylsulfonium compound and anaryldicycloalkylsulfonium compound.

The aryl group in the arylsulfonium compound is preferably an arylgroup, such as a phenyl group or a naphthyl group, or a hetroaryl group,such as an indole residue or a pyrrole residue, far preferably a phenylgroup or an indole residue. When the arylsulfonium compound has two ormore aryl groups, the two or more aryl groups may be the same ordifferent.

One or two alkyl groups which the arylsulfonium compound has as requiredare preferably 1-15C straight-chain or branched alkyl groups, withexamples including a methyl group, an ethyl group, a propyl group, ann-butyl group, a sec-butyl group and a t-butyl group.

One or two cycloalkyl groups which the arylsulfonium compound has asrequired are preferably 3-15C cycloalkyl groups, with examples includinga cyclopropyl group, a cyclobutyl group and a cyclohexyl group.

The aryl group, the alkyl group or the cycloalkyl group represented byany of R₂₀₁ to R₂₀₃ may have as a substituent an alkyl group(containing, e.g., 1 to 15 carbon atoms), a cycloalkyl group(containing, e.g., 3 to 15 carbon atoms), an aryl group (containing,e.g., 6 to 14 carbon atoms), an alkoxyl group (containing, e.g., 1 to 15carbon atoms), a halogen atom, a hydroxyl group or a phenylthio group.Suitable examples of such substituents include 1-12C straight-chain orbranched alkyl groups, 3-12C cycloalkyl groups and 1-12C straight-chain,branched or cyclic alkoxyl groups. Of these substituents, 1-4C alkylgroups and 1-4C alkoxyl groups are preferred over the others. One ofR₂₀₁ to R₂₀₃ may have such a substituent, or all of R₂₀₁ to R₂₀₃ mayhave such substituents. When R₂₀₁ to R₂₀₃ are aryl groups, it ispreferable that such a substituent is situated in the p-position of eacharyl group.

Then, the compound (ZI-2) is explained below.

The compound (ZI-2) is a compound represented by the formula (ZI) inwhich R₂₀₁ to R₂₀₃ each independently represent an organic group havingno aromatic ring. The term “aromatic ring” as used herein is intended toalso include aromatic rings containing hetero atoms.

The number of carbon atoms in an aromatic ring-free organic group aseach of R₂₀₁ to R₂₀₃ is generally from 1 to 30, preferably from 1 to 20.

Each of R₂₀₁ to R₂₀₂ is preferably an alkyl group, a cycloalkyl group,an allyl group or a vinyl group, far preferably a straight-chain,branched or cyclic 2-oxoalkyl group, or an alkoxycarbonylmethyl group,particularly preferably a straight-chain or branched 2-oxoalkyl group.

The alkyl group as each of R₂₀₁ to R₂₀₃ may have either a straight-chainor branched form, and it is preferably a 1-10C straight-chain orbranched group (e.g., a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group). The alkyl group as each of R₂₀₁ to R₂₀₃ isfar preferably a straight-chain or branched 2-oxoalkyl group, or analkoxycarbonylmethyl group.

The cycloalkyl group as each of R₂₀₁ to R₂₀₃ is preferably a 3-10Ccycloalkyl group (e.g., a cyclopentyl group, a cyclohexyl group, anorbornyl group). The cycloalkyl group as each of R₂₀₁ to R₂₀₃ is farpreferably a cyclic 2-oxoalkyl group.

Examples of a straight-chain, branched or cyclic 2-oxoalkyl groupsuitable as each of R₂₀₁ to R₂₀₃ include the groups having >C=0 in the2-positions of the alkyl or cycloalkyl groups recited above.

The alkoxy moiety in an alkoxycarbonylmethyl group as each of R₂₀₁ toR₂₀₃ is preferably a 1-5C alkoxyl group (such as a methoxy, ethoxy,propoxy, butoxy or pentoxy group).

Each of groups represented by R₂₀₁ to R₂₀₃ may further be substitutedwith a halogen atom, an alkoxyl group (containing, e.g., 1 to 5 carbonatoms), a hydroxyl group, a cyano group or a nitro group.

The compound (ZI-3) is a compound represented by the following formula(ZI-3), namely a compound having a phenacylsulfonium salt structure.

In the formula (ZI-3), R_(1c) to R_(5c) each represent a hydrogen atom,an alkyl group, a cycloalkyl group, an alkoxyl group or a halogen atomindependently.

R_(6c) and R_(7c) each represent a hydrogen atom, an alkyl group or acycloalkyl group independently.

R_(x) and R_(y) each represent an alkyl group, a cycloalkyl group, anallyl group or a vinyl group independently.

Any two or more of R_(1c) to R_(7c) may combine with one another to forma ring structure, and R_(x) and R_(y) may also combine with each otherto form a ring structure. In such a ring structure, an oxygen atom, asulfur atom, an ester linkage or an amide linkage may be contained. Thegroup formed by combining any two or more of R_(1c) to R_(7c) or bycombining R_(x) and R_(y) may be a butylene group or a pentylene group.

X—represents a non-nucleophilic anion, and examples thereof include thesame non-nucleophilic anions as examples of X—in formula (ZI) include.

The alkyl group as each of R_(1c) to R_(7c) may have either astraight-chain form or a branched form, and suitable examples thereofinclude 1-20C straight-chain or branched alkyl groups, preferably 1-12Cstraight-chain or branched alkyl groups (e.g., a methyl group, an ethylgroup, a straight-chain or branched propyl group, straight-chain orbranched butyl groups, straight-chain or branched pentyl groups).

Suitable examples of the cycloalkyl group as each of R_(1c) to R_(7c)include 3-8C cycloalkyl groups (e.g., a cyclopentyl group, a cyclohexylgroup).

The alkoxyl group as each of R_(1c) to R_(5c) may have either astraight-chain form, or a branched form, or a cyclic form, and examplesthereof include 1-10C alkoxyl groups, preferably 1-5C straight-chain andbranched alkoxyl groups (e.g., a methoxy group, an ethoxy group, astraight-chain or branched propoxy group, straight-chain or branchedbutoxy groups, straight-chain or branched pentoxy groups) and 3-8Ccycloalkoxyl groups (e.g., a cyclopentyloxy group, a cyclohexyloxygroup).

It is preferable that any of Ric to R5c is a straight-chain or branchedalkyl group, a cycloalkyl group, or a straight-chain, branched or cyclicalkoxyl group, and it is far preferable that the number of total carbonatoms in R_(1c), to R_(5c) is from 2 to 15. By meeting theserequirements, the solvent solubility can be enhanced, and development ofparticles during storage can be prevented.

Examples of the alkyl group as each of R_(x) and R_(y) include the samegroups as examples of the alkyl group as each of R_(1c) to R_(7c)include, preferably straight-chain and branched 2-oxoakyl groups andalkoxycarbonylmethyl groups.

Examples of the cycloalkyl group as each of R, and R_(y) include thesame groups as examples of the cycloalkyl group as each of R_(1c) toR_(7c) include, preferably cyclic 2-oxoakyl groups.

Examples of the straight-chain, branched and cyclic 2-oxoalkyl groupsinclude the groups having >C=0 at the 2-positions of the alkyl orcycloalkyl groups as R_(1c) to R_(7c).

Examples of the alkoxy moiety in the alkoxycarbonylmethyl group includesthe same alkoxyl groups as R_(1c) to R₅ each may represent.

Each of R_(x) and R_(y) is preferably an alkyl group containing at least4 carbon atoms, far preferably an alkyl group containing at least 6carbon atoms, further preferably an alkyl group containing at least 8carbon atoms.

In the formulae (ZII) and VIM, R₂₀₄ to R₂₀₇ each represent an arylgroup, an alkyl group or a cycloalkyl group independently.

The aryl group as each of R₂₀₄ to R₂₀₇ is preferably a phenyl group or anaphthyl group, far preferably a phenyl group.

The alkyl group as each of R₂₀₄ to R₂₀₇ may have either a straight-chainform or a branched form, with suitable examples including 1-10Cstraight-chain and branched alkyl groups (e.g., a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group).

The cycloalkyl group as each of R₂₀₄ to R₂₀₇ is preferably a 3-10Ccycloalkyl group (e.g., a cyclopentyl group, a cyclohexyl group, anorbornyl group).

The groups represented by R₂₀₄ to R₂₀₇ may have substituents. Examplesof such substituents include alkyl groups (e.g., those containing 1 to15 carbon atoms), cycloalkyl groups (e.g., those containing 3 to 15carbon atoms), aryl groups (e.g., those containing 6 to 15 carbonatoms), alkoxyl groups (e.g., those containing 1 to 15 carbon atoms),halogen atoms, a hydroxyl group and a phenylthio group.

X—represents a non-nucleophilic anion, and examples thereof include thesame non-nucleophilic anions as the X″ in the formula (ZI) canrepresent.

Of the compounds capable of generating an acid upon irradiation with anactinic ray or radiation, compounds represented by the followingformulae (ZIV), (ZV) and (ZVI) can be preferred examples.

In the formulae (ZIV) to (ZVI), Ar₃ and An₄ each represent an aryl groupindependently.

R₂₂₆ represents an alkyl group, a cycloalkyl group or an aryl group.

R₂₂₇ and R₂₂₈ each represent an alkyl group, a cycloalkyl group, an arylgroup or an electron-attracting group. R₂₂₇ is preferably an aryl group.R₂₂₈ is preferably an electron-attracting group, far preferably a cyanogroup or a fluoroalkyl group.

A represents an alkylene group, an alkenylene group or an arylene group.

Of the compounds capable of generating acids upon irradiation with anactinic ray or radiation, the compounds represented by (ZI) to (ZIII)are preferred to the others.

The Compound (B) is preferably a compound capable of generating analiphatic sulfonic acid having a fluorine atom or atoms or abenzenesulfonic acid having a fluorine atom or atoms upon irradiationwith an actinic ray or radiation.

It is preferable that the Compound (B) has a triphenylsulfoniumstructure.

It is far preferable that the Compound (B) is a triphenylsulfonium saltcompound having in its cation part an alkyl or cycloalkyl group free offluorine substituent.

Examples of particularly preferred ones among the compounds capable ofgenerating acids upon irradiation with an actinic ray or radiation areillustrated below.

Photo-acid generators can be used alone or as combinations of two ormore thereof. When two or more types of photo-acid generators are usedin combination, it is preferable to combine compounds which can generatetwo types of organic acids differing by at least two in the total numberof constituent atoms except hydrogen atoms.

The content of photo-acid generators is preferably from 0.1 to 20 mass%, far preferably from 0.5 to 10 mass %, further preferably from 1 to 7mass %, based on the total solids in the resist composition. Byadjusting the content of photo-acid generators to fall within theforegoing range, the exposure latitude at the time of resist patternformation can be improved and the crosslinking reactivity with materialsfor forming a cross-linked layer can be increased.

(C) Solvent

Examples of a solvent which can be used in dissolving each of theingredients to prepare a resist composition include organic solvents,such as an alkylene glycol monoalkyl ether carboxylate, an alkyleneglycol monoalkyl ether, an alkyl lactate, an alkyl alkoxypropionate, a4-10C cyclic lactone, a 4-10C monoketone compound which may contain aring, an alkylene carbonate, an alkyl alkoxyacetate and an alkylpyruvate.

Suitable examples of an alkylene glycol monoalkyl ether carbonateinclude propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, propylene glycol monopropyl ether acetate,propylene glycol monobutyl ether acetate, propylene glycol monomethylether propionate, propylene glycol monoethyl ether propionate, ethyleneglycol monomethyl ether acetate, and ethylene glycol monoethyl etheracetate.

Suitable examples of an alkylene glycol monoalkyl ether includepropylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monopropyl ether, propylene glycol monobutyl ether,ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether.

Suitable examples of an alkyl lactate include methyl lactate, ethyllactate, propyl lactate, and butyl lactate.

Suitable examples of an alkyl alkoxypropionate include ethyl3-ethoxypropionate, methyl 3-methoxypropionate, methyl3-ethoxypropionate, and ethyl 3-methoxypropionate.

Suitable examples of a 4-10C cyclic lactone include (3-propiolactone,(3-butyrolactone, y-butyrolactone, a-methyl-y-butyrolactone,(3-methyl-y-butyrolactone, y-valerolactone, y-caprolactone, y-octanoiclactone, and a-hydroxy-y-butyrolactone.

Suitable examples of a 4-10C monoketone compound which may contain aring include 2-butanone, 3-methylbutanone, pinacolone, 2-pentanone,3-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone,2-methyl-3-pentanone, 4,4-dimethyl-2-pentanone,2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone, 2-hexanone,3-hexanone, 5-methyl-3-hexanone, 2-heptanone, 3-heptanone, 4-heptanone,2-methyl-3-heptanone, 5-methyl-3-heptanone, 2,6-dimethyl-4-heptanone,2-octanone, 3-octanone, 2-nonanone, 3-nonanone, 5-nonanone, 2-decanone,3-decanone, 4-decanone, 5-hexene-2-one, 3-pentene-2-one, cyclopentanone,2-methylcyclopentanone, 3-methylcyclopentanone,2,2-dimethylcyclopentanone, 2,4,4-trimethylcyclopentanone,cyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,2-dimethylcyclohexanone,2,6-dimethylcyclohexanone, 2,2,6-trimethylcyclohexanone, cycloheptanone,2-methylcycloheptanone, and 3-methylcycloheptanone.

Suitable examples of an alkylene carbonate include propylene carbonate,vinylene carbonate, ethylene carbonate, and butylene carbonate.

Suitable examples of an alkyl alkoxyacetate includeacetate-2-methoxyethyl, acetate-2-ethoxyethyl,acetate-2-(2-ethoxyethoxy)ethyl, acetate-3-methoxy-3-methylbutyl, andacetate-1-methoxy-2-propyl.

Suitable examples of an alkyl pyruvate include methyl pyruvate, ethylpyruvate, and propyl pyruvate.

Examples of a solvent used to advantage include solvents having boilingpoints of 130° C. or above at ordinary temperatures and under normalatmospheric pressure. More specifically, such solvents includecyclopentanone, y-butyrolactone, cyclohexanone, ethyl lactate, ethyleneglycol monoethyl ether acetate, propylene glycol monomethyl etheracetate, ethyl 3-ethoxypropionate, ethyl pyruvate,acetate-2-ethoxyethyl, acetate-2-(2-ethoxyethoxy)ethyl and propylenecarbonate.

In the invention, the solvents recited above may be used alone or ascombinations of two or more thereof.

The solvent used in the invention may also be a mixture of a solventhaving a hydroxyl group in its structure and a solvent having nohydroxyl group.

Examples of a solvent having a hydroxyl group include ethylene glycol,ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,propylene glycol, propylene glycol monomethyl ether, propylene glycolmonoethyl ether, and ethyl lactate. Of these solvents, propylene glycolmonomethyl ether and ethyl lactate are especially preferred to theothers.

Examples of a solvent having no hydroxyl group include propylene glycolmonomethyl ether acetate, ethyl ethoxypropionate, 2-heptanone,y-butyrolactone, cyclohexanone, butyl acetate, N-methylpyrrolidone,N,N-dimethylacetamide, and dimethyl sulfoxide. Of these solvents,propylene glycol monomethyl ether acetate, ethyl ethoxypropionate,2-heptanone, y-butyrolactone, cyclohexanone and butyl acetate are farpreferred to the others, and propylene glycol monomethyl ether acetate,ethyl ethoxypropionate and 2-heptanone are used to particular advantage.

The mixing ratio (by mass) between the solvent containing a hydroxylgroup and the solvent containing no hydroxyl group is from 1/99 to 99/1,preferably from 10/90 to 90/10, far preferably from 20/80 to 60/40. Amixed solvent containing a solvent having no hydroxyl group in aproportion of 50 weight % or above is particularly preferred from theviewpoint of coating evenness.

The solvent used in the invention is preferably a mixture of two or morekinds of solvents including propylene glycol monomethyl ether acetate.

(E) Basic Compound

For reduction of performance changes occurring with the passage of timefrom exposure to heating, it is appropriate that the resist compositionfor use in the invention contain (E) a basic compound.

Examples of a compound suitable as the basic compound include compoundshaving structures represented by the following (A) to (E).

In the formulae (A) and (E), R²⁰⁰, R²⁰¹ and R²⁰² may be the same ordifferent, and each of them represents a hydrogen atom, an alkyl group(preferably a 1-20C alkyl group), a cycloalkyl group (preferably a 3-20Ccycloalkyl group) or an aryl group (containing 6 to 20 carbon atoms).Herein, R²⁰¹ and R²⁰² may combine with each other to form a ring.

When the foregoing alkyl group has a substituent, a 1-20C aminoalkylgroup, a 1-20C hydroxyalkyl group or a 1-20C cyanoalkyl group issuitable as the substituted alkyl group.

In the formula (E), R²⁰³, R²⁰⁴, R²⁰⁵ and R²⁰⁶ may be the same ordifferent, and each of them represents a 1-20C alkyl group.

The alkyl groups in the formulae (A) to (E) are preferably unsubstitutedalkyl groups.

Examples of preferred basic compounds include guanidine,aminopyrrolidine, pyrazole, pyrazoline, piperazine, aminomorpholine,aminoalkylmorpholine and piperidine. Examples of far preferred compoundsinclude compounds having an imidazole structure, a diazabicyclostructure, an onium hydroxide structure, an onium carboxylate structure,a trialkylamine structure, an aniline structure and a pyridinestructure, respectively; an alkylamine derivative having a hydroxylgroup and/or an ether linkage; and an aniline derivative having ahydroxyl group and/or an ether linkage.

Examples of the compound having an imidazole structure includeimidazole, 2,4,5-triphenylimidazole and benzimidazole. Examples of thecompound having a diazabicyclo structure include 1,4-diazabicyclo[2.2.2]octane, 1,5-diazabicyclo[4.3.0]nona-5-ene and1,8-diazabicyclo[5.4.0]undeca-7-ene. Examples of the compound having anonium hydroxide structure include triarylsulfonium hydroxides,phenacylsulfonium hydroxides and sulfonium hydroxides having 2-oxoalkylgroups, and more specifically, they include triphenylsulfoniumhydroxide, tris(t-butylphenyl)sulfonium hydroxide,bis(t-butylphenyl)iodonium hydroxide, phenacylthiophenium hydroxide and2-oxopropylthiophenium hydroxide. The compound having an oniumcarboxylate structure is a compound having the structure correspondingto the substitution of carboxylate for the anion moiety of the compoundhaving an onium hydroxide structure, with examples including acetate,adamantane-1-carboxylate and perfluoroalkylcarboxylates. Examples of thecompound having a trialkylamine structure include tri(n-butyl)amine andtri(n-octyl)amine. Examples of the aniline compound include2,6-diisopropylaniline, N,N-dimethylaniline, N,N-dibutylaniline andN,N-dihexylaniline. Examples of the alkylamine derivative having ahydroxyl group and/or an ether linkage include ethanolamine,diethanolamine, triethanolamine and tris(methoxyethoxyethyl)amine. Anexample of the aniline derivative having a hydroxyl group and/or anether linkage is N,N-bis(hydroxyethyl)aniline.

These basic compounds are used alone or as combinations of two or morethereof.

The amount of basic compounds used is generally from 0.001 to 10 mass %,preferably 0.01 to 5 mass %, based on the total solids in the resistcomposition.

The ratio between the amount of acid generator(s) used and the amount ofbasic compound(s) used in the composition, the acid generator/basiccompound ratio (by mole), is preferably from 2.5 to 300. Morespecifically, it is appropriate that the ratio by mole be adjusted to atleast 2.5 in point of sensitivity and resolution, and that it beadjusted to at most 300 from the viewpoint of preventing degradation inresolution by thickening of resist patterns with the passage of timefrom the end of exposure to heating treatment. The acid generator/basiccompound ratio (by mole) is preferably from 5.0 to 200, far preferablyfrom 7.0 to 150.

(F) Surfactant

It is preferable that the resist composition for use in the inventionfurther contains (F) a surfactant, specifically a surfactant containingat least one fluorine atom and/or at least one silicon atom (either afluorine-containing surfactant, or a silicon-containing surfactant, or asurfactant containing both fluorine and silicon atoms), or a combinationof at least two of these surfactants.

Incorporation of such a surfactant in the resist composition for use inthe invention allows production of resist patterns having strongadhesion and reduced development defect while ensuring the compositionboth satisfactory sensitivity and high resolution in the case of usingan exposure light source of 250 nm or below, especially 220 nm or below.

Examples of a surfactant containing at least one fluorine atom and/or atleast one silicon atom include the surfactants disclosed inJP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950,JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JP-A-9-54432, JP-A-9-5988,JP-A-2002-277862, and U.S. Pat. Nos. 5,405,720, 5,360,692, 5,529,881,5,296,330, 5,436,098, 5,576,143, 5,294,511 and 5,824,451. In addition,the following commercially available surfactants can also be used asthey are.

Examples of commercial surfactants which can be used include fluorine-or silicon-containing surfactants, such as EFTOP EF301 and EF303(produced by Shin-Akita Kasei K.K.), Florad FC430, 431 and 4430(produced by Sumitomo 3M, Inc.), Megafac F171, F173, F176, F189, F113,F110, F177, F120 and R08 (produced by Dainippon Ink & Chemicals, Inc.),Surflon S-382, SC101, 102, 103, 104, 105 and 106 (produced by AsahiGlass Co., Ltd.), Troysol S-366 (produced by Troy Chemical Industries,Inc.), GF-300 and GF-150 (produced by Toagosei Co., Ltd.), Surflon S-393(produced by Seimi Chemical Co., Ltd.), EFTOP EF121, EF122A, EF122B,RF122C, EF125M, EF135M, EF351, EF352, EF801, EF802 and EF601 (producedby JEMCO Inc.), PF636, PF656, PF6320 and PF6520 (produced by OMNOVASolutions Inc.), and FTX-204D, 208G, 218G, 230G, 204D, 208D, 212D, 218Dand 222D (produced by NEOS). Moreover, organosiloxane polymer KP-341(produced by Shin-Etsu Chemical Co., Ltd.) can be used as asilicon-containing surfactant.

In addition to the heretofore known surfactants as recited above,surfactants utilizing polymers having fluorinated aliphatic groupsderived from fluorinated aliphatic compounds synthesized by atelomerization method (also referred to as a telomer method) or anoligomerization method (also referred to as an oligomer method) can beused. These fluorinated aliphatic compounds can be synthesized accordingto the methods disclosed in JP-A-2002-90991.

The polymers having fluorinated aliphatic groups are preferablycopolymers of fluorinated aliphatic group-containing monomers and(poly(oxyalkylene)) acrylates and/or (poly(oxyalkylene)) methacrylates,wherein the fluorinated aliphatic group-containing units may bedistributed randomly or in blocks. Examples of such a poly(oxyalkylene)group include a poly(oxyethylene) group, a poly(oxypropylene) group anda poly(oxybutylene) group. In addition, the poly(oxyalkylene) group maybe a unit containing alkylene groups of different chain lengths in itsoxyalkylene chain, such as poly(oxyethylene block/oxypropyleneblock/oxyethylene block combination) and poly(oxyethyleneblock/oxypropylene block combination). Further, the copolymers offluorinated aliphatic group-containing monomers and (poly(oxyalkylene))acrylates (or methacrylates) may be not only binary copolymers but alsoternary or higher copolymers prepared using in each individualcopolymerization at least two different kinds of fluorinated aliphaticgroup-containing monomers or/and at least two different kinds of(poly(oxyalkylene)) acrylates (or methacrylates) at the same time.

Examples of commercially available surfactants of such types includeMegafac F178, F-470, F-473, F-475, F-476 and F-472 (produced byDainippon Ink & Chemicals, Inc.). Additional examples of surfactants ofsuch types include a copolymer of C6F13 group-containing acrylate (ormethacrylate) and poly(oxyalkylene) acrylate (or methacrylate), and acopolymer of C3F7 group-containing acrylate (or rnethacrylate),poly(oxyethylene) acrylate (or methacrylate) and poly(oxypropylene)acrylate (or methacrylate).

Alternatively, it is also possible to use surfactants other thansurfactants containing fluorine and/or silicon atoms. Examples of suchsurfactants include nonionic surfactants, such as polyoxyethylene alkylethers (e.g., polyoxyethylene lauryl ether, polyoxyethylene stearylether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether),polyoxyethylene alkyl aryl ethers (e.g., polyoxyethylene octyl phenolether, polyoxyethylene nonyl phenol ether),polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acidesters (e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan monooleate, sorbitan trioleate, sorbitantristearate), and polyoxyethylene sorbitan fatty acid esters (e.g.,polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan trioleate, polyoxyethylene sorbitan tristearate).

These surfactants may be used alone or as combinations of two or morethereof.

The amount of a surfactant (F) used is preferably from 0.01 to 10 mass%, preferably 0.1 to 5 mass %, based on the total ingredients (exclusiveof a solvent) in the resist composition.

(G) Onium Salt of Carboxylic Acid

The resist composition for use in the invention may further contain (G)an onium salt of carboxylic acid. Examples of such an onium salt ofcarboxylic acid (G) include sulfonium carboxylates, iodoniumcarboxylates and ammonium carboxylates. Of these onium salts, iodoniumsalts and sulfonium salts are especially preferred. In addition, it ispreferable that neither aromatic group nor carbon-carbon double bond ispresent in the carboxylate residue of an onium carboxylate (G) used inthe invention. As the anion part of (G), 1-30C straight-chain andbranched alkyl carboxylate anions and mononuclear or polynuclearcycloalkyl carboxylate anions are especially suitable. Of these anions,the carboxylate anions whose alkyl groups are partially or entirelysubstituted with fluorine atoms are preferred over the others. Inaddition, those alkyl chains may contain oxygen atoms. Incorporation ofan onium salt having such a carboxylate anion into a resist compositioncan ensure the resist composition transparency to light with wavelengthsof 220 nm or below, and allows increases in sensitivity and resolution,and improvements in iso/dense bias and exposure margin.

Examples of a fluorinated carboxylate anion include a fluoroacetateanion, a difluoroacetate anion, a trifluoroacetate anion, apentafluoropropionate anion, a heptafluorobutyrate anion, anonafluoropentanate anion, a perfluorododecanate anion, aperfluorotridecanate anion, a perfluorocyclohexanecarboxylate anion anda 2,2-bistrifluoromethylpropionate anion.

The onium carboxylate (G) as recited above can be synthesized byallowing an onium hydroxide, such as sulfonium hydroxide, iodoniumhydroxide or ammonium hydroxide, and a carboxylic acid to react withsilver oxide in an appropriate solvent.

The suitable content of an onium salt of carboxylic acid (G) in acomposition is generally from 0.1 to 20 mass %, preferably from 0.5 to10 mass %, far preferably from 1 to 7 mass %, based on the total solidsin the composition.

(H) Other Additives

The resist composition for use in the invention can further contain, onan as needed basis, dyes, plasticizers, photosensitizers, lightabsorbents, alkali-soluble resins, dissolution inhibitors and compoundswhich can promote dissolution in developers (e.g., phenol compoundshaving molecular weights of 1,000 or below, alicyclic or aliphaticcompounds having carboxyl groups).

The phenol compounds which are 1,000 or below in molecular weight can beeasily synthesized by persons skilled in the art when they refer to themethods as disclosed in JP-A-4-122938, JP-A-2-28531, U.S. Pat. No.4,916,210 and European Patent No. 219,294.

Examples of alicyclic or aliphatic compounds having carboxyl groupsinclude carboxylic acid derivatives having steroid structures, such ascholic acid, deoxycholic acid and lithocholic acid, adamantanecarboxylicacid derivatives, adamantanedicarboxylic acid, cyclohexanecarboxylicacid and cyclohexanedicarboxylic acid, but they are not limited to thecompounds recited above.

A protective film composition for forming a protective film to be usedin the pattern formation method of the invention is explained below.

<Protective Film Composition>

In the present pattern formation method, a film of protective filmcomposition is formed on the top of a resist film prior to immersionexposure for the purpose of preventing direct contact between animmersion liquid and the resist film, thereby inhibiting resistperformance degradation from the immersion liquid penetrated into theinterior of the resist film and ingredients eluted from the resist filminto the immersion liquid, and further for avoiding lens contaminationwith ingredients seeping out of the resist film into the immersionliquid.

For formation of a uniform film of protective film composition on theresist film, it is appropriate that a constituent resin of theprotective film composition applied in the present pattern formationmethod be used in a state of being dissolved in a solvent.

For contribution to good-quality pattern formation without causingdissolution of resist film, it is appropriate that the protective filmcomposition for use in the invention contain a solvent in which theresist film is insoluble, and it is more appropriate that the solventused in the composition be different from the constituent solvent of anegative developer used. From the viewpoint of preventing elution intoan immersion liquid, it is preferable that the composition is lower inimmersion liquid solubility, and it is far preferable that thecomposition is lower in water solubility. The expression “lower inimmersion liquid solubility” as used in the specification means beinginsoluble in the immersion liquid. Likewise, the expression “lower inwater solubility” means being insoluble in water. In addition, from theviewpoints of volatility and coating suitability, it is preferable thatthe boiling point of the solvent in the composition is from 90° C. to200° C.

To take an example from water solubility, the expression “lower inimmersion liquid solubility” means that, when film formed by applying aprotective film composition to a silicon wafer surface and drying thecomposition is immersed in purified water at 23° C. for 10 minutes andthen dried, the reduction rate of film thickness is within 3% of theinitial film thickness (typically 50 nm).

From the viewpoint of applying a uniform protective film, the solvent isused in an amount required for adjustment of the solids concentration toa range of 0.01 to 20 mass %, preferably 0.1 to 15 mass %, particularlypreferably 1 to 10 mass %.

The solvent usable in the protective film composition has no particularrestriction so long as it can dissolve Resin (X) described hereinafter,but it cannot dissolve the resist film. However, an alcohol solvent, afluorinated solvent and a hydrocarbon solvent can be used to advantage,and a non-fluorinated alcohol solvent can be used to greater advantage.In such solvents, the resist film has further reduced solubility. So,application of the protective film composition to the resist film doesnot cause dissolution of the resist film, and a more uniform protectivefilm can be formed.

In point of coating suitability, the alcohol solvent is preferably amonohydric alcohol, far preferably a monohydric 4-8C alcohol. Themonohydric 4-8C alcohol may be of a straight-chain, branched or cyclicform, preferably a straight-chain or branched form. Examples of such analcohol solvent include 1-butanol, 2-butanol, 3-methyl-1-butanol,isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 1-hexanol,1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol,3-heptanol, 3-octanol and 4-octanol. Of these alcohol solvents,1-butanol, 1-hexanol, 1-pentanol and 3-methyl-1-butanol are preferredover the others.

Examples of a fluorinated solvent include2,2,3,3,4,4-hexafluoro-1-butanol, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol,2,2,3,3,4,4,5,5,6,6-decafluoro-1-hexanol,2,2,3,3,4,4-hexafluoro-1,5-pentanedio1,2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol,2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-dio-1,2-fluoroanisole,2,3-difluoroanisole, perfluorohexane, perfluoroheptane,perfluoro-2-pentanone, perfluoro-2-butyltetrahydrofuran,perfluorotetrahydrofuran, perfluorotributylamine, andperfluorotetrapentylamine. Of these solvents, the fluorinated alcoholsolvents and the fluorinated hydrocarbon solvents are used to advantage.

Examples of the hydrocarbon solvent include aromatic hydrocarbonsolvents, such as toluene, xylene and anisole, and aliphatic hydrocarbonsolvents, such as n-heptane, n-nonane, n-octane, n-decane,2-methylheptane, 3-methyl heptane, 3,3-dimethylhexane and2,3,4-trimethylpentane.

These solvents may be used alone or as combinations of two or morethereof

When solvents other than those recited above are mixed, the proportionof the solvents mixed is generally from 0 to 30 mass %, preferably from0 to 20 mass %, far preferably from 0 to 10 mass %, based on the totalsolvents in the protective film composition. By mixing with solventsother than those recited above, the solubility of the resist film, thesolubility of the resin in the protective film composition andcharacteristics of elution from the resist film can be adjusted asappropriate.

For ensuring arrival of exposure light at the resist film via theprotective film, it is appropriate that the resin be transparent to anexposure light source used. When ArF immersion exposure is adopted, itis preferable in point of transparency to ArF light that the resin hasno aromatic group.

The resin is preferably a Resin (X) which has repeating units derivedfrom a monomer containing either at least one fluorine atom, or at leastone silicon atom, or both, far preferably a water-insoluble Resin (X′)which has repeating units derived from a monomer containing either atleast one fluorine atom, or at least one silicon atom, or both. Byhaving repeating units derived from a monomer containing either at leastone fluorine atom, or at least one silicon atom, or both, the resin canattain good solubility in a negative developer, and the effects of theinvention can be fully achieved.

The Resin (X) may contain fluorine atoms or silicon atoms in its mainchain or in a state that those atoms are substituted for hydrogen atomsin its side chains. The Resin (X) is preferably a resin having as itspartial structures fluorinated alkyl groups, fluorinated cycloalkylgroups or fluorinated aryl groups.

The fluorinated alkyl groups (preferably containing 1 to 10 carbonatoms, far preferably 1 to 4 carbon atoms) are straight-chain orbranched alkyl groups which each have at least one fluorine atomsubstituted for a hydrogen atom, which may further have othersubstituents.

The fluorinated cycloalkyl groups are mononuclear or polynuclearcycloalkyl groups which each have at least one fluorine atom substitutedfor a hydrogen atom, which may further have other substituents.

The fluorinated aryl groups are aryl groups, such as a phenyl group anda naphthyl group, which each have a fluorine atom substituted for atleast one hydrogen atom and may further have other substituents.

Examples of a fluorinated alkyl group, a fluorinated cycloalkyl group ora fluorinated aryl group are illustrated below, but these examplesshould not be construed as limiting the scope of the invention.

In the above formulae (f2) and (f3), R₅₇ to R₆₄ each represent ahydrogen atom, a fluorine atom or an alkyl group independently, providedthat at least one of R₅₇ to R₆₁ and at least one of R₆₂ to R₆₄ arefluorine atoms or alkyl groups (preferably containing 1 to 4 carbonatoms) each having a fluorine atom substituted for at least one hydrogenatom. All of R₅₇ to R₆₁ are preferably fluorine atoms. Both R₆₂ and R₆₃are preferably alkyl groups (preferably containing 1 to 4 carbon atoms)each having a fluorine atom substituted for at least one hydrogen atom,far preferably perfluoroalkyl groups having 1 to 4 carbon atoms. R₆₂ andR₆₃ may combine with each other to form a ring.

Examples of a group represented by the formula (f2) include ap-fluorophenyl group, a pentafluorophenyl group and a3,5-di(trifluoromethyl)phenyl group.

Examples of a group represented by the formula (f3) include atrifluoroethyl group, a pentafluoropropyl group, a pentafluoroethylgroup, a pentafluorobutyl group, a hexafluoroisopropyl group, ahexafluoro(2-methyl)isopropyl group, a nonafluorobutyl group, anoctafluoroisobutyl group, a nonafluorohexyl group, a nonafluoro-t-butylgroup, a perfluoroisopentyl group, a perfluorooctyl group, aperfluoro(trimethyl)hexyl group, a 2,2,3,3-tetrafluorocyclobutyl groupand a perfluorohexyl group. Of these groups, a hexafluoroisopropylgroup, a heptafluoroisopropyl group, a hexafluoro(2-methyl)isopropylgroup, an octafluoroisobutyl group, a nonafluoro-t-butyl group and aperfluoroisopentyl group are preferable to the others, and ahexafluoroisopropyl group and a heptafluoroisopropyl group are farpreferred.

The Resin (X) containing silicon atoms in its partial structures ispreferably a resin having alkylsilyl structures (preferablytrialkylsilyl groups) or cyclic siloxane structures as its partialstructures.

Examples of an alkylsilyl or cyclic siloxane structure include groupsrepresented by the following formula (CS-1), (CS-2) or (CS-3).

In the formulae (CS-1) to (CS-3), R₁₂ to R₂₆ are independent of oneanother, and each represent a straight-chain or branched alkyl group(preferably containing 1 to 20 carbon atoms) or a cycloalkyl group(preferably containing 3 to 20 carbon atoms).

L₃ to L₅ each represent a single bond or a divalent linkage group.Examples of such a divalent linkage group include an alkylene group, aphenylene group, an ether group, a thioether group, a carbonyl group, anester group, an amide group, an urethane group, an urea group, andcombinations of two or more of the groups recited above.

n represents an integer of 1 to 5.

An example of the Resin (X) is a resin having repeating units of atleast one kind selected from among those represented by the followingformulae (C-I) to (C-V).

In the formulae (C-I) to (C-V), R1 to R3 are independent of one another,and each represents a hydrogen atom, a fluorine atom, a 1-4Cstraight-chain or branched alkyl group, or a 1-4C straight-chain orbranched fluoroalkyl group.

W₁ and W₂ each represent an organic group having at least either afluorine atom or a silicon atom.

R₄ to R₇ are independent of one another, and each represents a hydrogenatom, a fluorine atom, a 1-4C straight-chain or branched alkyl group, ora 1-4C straight-chain or branched fluoroalkyl group; however at leastone of the substituents R₄ to R₇ is required to be a fluorine atom.Alternatively, R₄ and R₅, or R₆ and R₇ may combine with each other toform a ring.

R₉ represents a hydrogen atom, or a 1-4C straight-chain or branchedalkyl group.

R₉ represents a 1-4C straight-chain or branched alkyl group, or a 1-4Cstraight-chain or branched fluoroalkyl group.

L₁ and L₂ each represent a single bond or a divalent linkage group,which each have the same meaning as the foregoing L₃ to L₅ each have.

Q represents a mononuclear or polynuclear cyclic aliphatic group. Morespecifically, it represents atoms including two carbon atoms bondedtogether (C—C) and forming an alicyclic structure.

R₃₀ and R₃₁ each represent a hydrogen atom or a fluorine atomindependently. R₃₂ and R₃₃ each represent an alkyl group, a cycloalkylgroup, a fluorinated alkyl group or a fluorinated cycloalkyl groupindependently.

However, the repeating unit represented by the formula (C-V) is requiredto have at least one fluorine atom in at least one of the substituentsR₃₀ to R₃₃.

It is preferable that the Resin (X) has repeating units represented bythe formula (C—I), and it is far preferable that the Resin (X) hasrepeating units represented by the following formulae (C-Ia) to (C-Id).

In the formulae (C-Ia) to (C-Id), R₁₀ and R₁₁ each represent a hydrogenatom, a fluorine atom, a 1-4C straight-chain or branched alkyl group, ora 1-4C straight-chain or branched fluorinated alkyl group.

W₃ to W₆ each represent an organic group having at least either one ormore fluorine atoms, or one or more silicon atoms.

When W₁ to W₆ are fluorine-containing organic groups, each organic groupis preferably a 1-20C straight-chain, branched or cyclic fluorinatedalkyl group, or a 1-20C straight-chain, branched or cyclic fluorinatedalkoxyl group.

Examples of the fluorinated alkyl group of W₁ to W₆ each include atrifluoroethyl group, a pentafluoropropyl group, a hexafluoroisopropylgroup, a hexafluoro(2-methyl)isopropyl group, a heptafluorobutyl group,a heptafluoroisopropyl group, an octafluoroisobutyl group, anonafluorohexyl group, a nonafluoro-t-butyl group, a perfluoroisopentylgroup, a perfluorooctyl group and a perfluoro(trimethyl)hexyl group.

When W₁ to W₆ are silicon-containing organic groups, each organic grouppreferably has an alkylsilyl or cyclic siloxane structure. Examples ofsuch a group include groups represented by the formulae (CS-1), (CS-2)and (CS-3).

Examples of a repeating unit represented by the formula (C-I) areillustrated below. In the following structural formulae, X represents ahydrogen atom, —CH₃, —F or —CF₃.

The Resin (X) may further have repeating units represented by thefollowing formula (Ia) for the purpose of adjusting its solubility in anegative developer.

In the formula (Ia), Rf represents a fluorine atom or a fluorinatedalkyl group in which at least one hydrogen atom is substituted with afluorine atom. R₁ represents an alkyl group. R₂ represents a hydrogenatom or an alkyl group.

The fluorinated alkyl group of Rf in the formula (Ia) is preferably agroup containing 1 to 3 carbon atoms, far preferably a trifluoromethylgroup.

The alkyl group of R₁ is preferably a 3-10C straight-chain or branchedalkyl group, far preferably a 3-10C branched alkyl group.

The alkyl group of R₂ is preferably a 1-10C straight-chain or branchedalkyl group, far preferably a 3-10C straight-chain or branched alkylgroup.

Examples of a repeating unit represented by the formula (Ia) areillustrated below, but the invention should not be construed as beingrestricted by these examples.

X═F or CF₃

Furthermore, the Resin (X) may also have repeating units represented bythe following formula (III).

In the formula (III), R₄ represents an alkyl group, a cycloalkyl group,an alkenyl group, a cycloalkenyl group, a trialkylsilyl group or a grouphaving a cyclic siloxane structure, and L6 represents a single bond or adivalent linkage group.

The alkyl group of R₄ in the formula (III) is preferably a 3-20Cstraight-chain or branched alkyl group.

The cycloalkyl group is preferably a 3-20C cycloalkyl group.

The alkenyl group is preferably a 3-20C alkenyl group.

The cycloalkenyl group is preferably a 3-20C cycloalkenyl group.

The trialkylsilyl group is preferably a 3-20C trialkylsilyl group.

The group having a cyclic siloxane structure is preferably a grouphaving a 3-20C cyclic siloxane structure.

The divalent linkage group of L₆ is preferably an alkylene group(preferably containing 1 to 5 carbon atoms) or an oxy group (—O—).

The Resin (X) may have lactone groups, ester groups, acid anhydridegroups, and groups similar to the acid-decomposable groups in a Resin(A). The Resin (X) may further have repeating units represented by thefollowing formula (VIII).

In the formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents ahydrogen atom, a hydroxyl group, an alkyl group or —OSO₂—R₄₂. R₄₂represents an alkyl group, a cycloalkyl group or a camphor residue. Thealkyl groups of R₄₁ and R₄₂ may be substituted with halogen atoms(preferably fluorine atoms) or so on.

It is preferable that the Resin (X) has repeating units (d) derived froma monomer containing an alkali-soluble group. Introduction of suchrepeating units allows control of immersion liquid solubility andcoating solvent solubility of the Resin (X). Examples of thealkali-soluble group include groups containing a phenolic hydroxylgroup, a carboxylic acid group, a fluorinated alcohol group, a sulfonicacid group, a sulfonamido group, a sulfonylimido group, an(alkylsulfonyl)(alkylcarbonyl)methylene group, an(alkylsulfonyl)(alkylcarbonyl)imido group, a bis(alkylcarbonyl)methylenegroup, a bis(alkylcarbonyl)imido group, a bis(alkylsulfonyl)methylenegroup, a bis(alkylsulfonyl)imido group, a tris(alkylcarbonyl)methylenegroup and a tris(alkylsulfonyl)methylene group.

The monomer containing an alkali-soluble group is preferably a monomerwhose acid dissociation index pKa is 4 or above, far preferably amonomer whose pKa is from 4 to 13, and especially preferably a monomerwhose pKa is from 8 to 13. When the Resin (X) has repeating unitsderived from a monomer whose pKa is 4 or above, swelling of theprotective film during both negative development and positivedevelopment is restrained, and good developability is achieved in notonly the case of using a negative developer but also the case of using aweak-base alkali developer as a positive developer.

Data on the acid dissociation constant Ka can be found in Kagaku Binran(II) (Handbook of Chemistry), revised 4th Ed., edited by The ChemicalSociety of Japan, published by Maruzen Co., Ltd. in 1993, and the pKavalues of monomers containing alkali-soluble groups can be measured at25° C., e.g., by use of an infinite dilution solvent.

Monomers having pKa of 4 or above are not limited to particular ones,and they may include monomers having acid groups (alkali-solublegroups), such as a phenolic hydroxyl group, a sulfonamido group, a—COCH₂CO—group, a fluoroalcohol group and a carboxylic acid group. Ofthese monomers, a monomer having a fluoroalcohol group is particularlypreferable to the others. The fluoroalcohol group is a fluoroalkyl groupsubstituted with at least one hydroxyl group, which contains preferably1 to 10 carbon atoms, far preferably 1 to 5 carbon atoms. Examples ofsuch a fluoroalcohol group include —CF₂OH, —CH₂CF₂OH, —CH₂CF₂CF₂OH,—C(CF₃)₂OH, —CF₂CF(CF₃)OH, and —CH₂C(CF₃)₂OH. Of these fluoroalcoholgroups, hexafluoroisopropanol group in particular is preferred.

The total proportion of repeating units derived from monomers containingalkali-soluble groups in the Resin (X) is preferably from 0 to 90 mole%, far preferably from 0 to 80 mole %, further preferably from 0 to 70mole %, with respect to all the repeating units constituting the Resin(X).

A monomer having an alkali-soluble group may contain one acid group ormore than one acid group. The number of acid groups contained in each ofrepeating units derived from such a monomer is preferably 2 or more, farpreferably from 2 to 5, particularly preferably 2 or 3.

Suitable examples of a repeating unit derived from a monomer having analkali-soluble group include, but not limited to, the repeating unitsillustrated below.

The Resin (X) is preferably a resin selected from the following resins(X-1) to (X-8).

(X-1): A resin that has (a) repeating units containing fluoroalkylgroups (which each preferably contain 1 to 4 carbon atoms), preferably aresin constituted of the repeating units (a) alone.

(X-2): A resin that has (b) repeating units containing trialkylsilylgroups or cyclic siloxane structures, preferably a resin having only therepeating units (b).

(X-3): A resin that has (a) repeating units containing fluoroalkylgroups (which each preferably contain 1 to 4 carbon atoms) and (c)repeating units containing branched alkyl groups (which each preferablycontain 4 to 20 carbon atoms), cycloalkyl groups (which each preferablycontain 4 to 20 carbon atoms), branched alkenyl groups (which eachpreferably contain 4 to 20 carbon atoms), cycloalkenyl groups (whicheach preferably contain 4 to 20 carbon atoms) or aryl groups (which eachpreferably contain 4 to 20 carbon atoms), preferably a copolymer resinconstituted of the repeating units (a) and the repeating units (c).

(X-4): A resin that has (b) repeating units containing trialkylsilylgroups or cyclic siloxane structures and (c) repeating units containingbranched alkyl groups (which each preferably contain 4 to 20 carbonatoms), cycloalkyl groups (which each preferably contain 4 to 20 carbonatoms), branched alkenyl groups (which each preferably contain 4 to 20carbon atoms), cycloalkenyl groups (which each preferably contain 4 to20 carbon atoms) or aryl groups (which each preferably contain 4 to 20carbon atoms), preferably a copolymer resin constituted of the repeatingunits (b) and the repeating units (c).

(X-5): A resin that has (a) repeating units containing fluoroalkylgroups (which each preferably contain 1 to 4 carbon atoms) and (b)repeating units containing trialkylsilyl groups or cyclic siloxanestructures, preferably a copolymer resin constituted of the repeatingunits (a) and the repeating units (b).

(X-6): A resin that has (a) repeating units containing fluoroalkylgroups (which each preferably contain 1 to 4 carbon atoms), (b)repeating units containing trialkylsilyl groups or cyclic siloxanestructures and (c) repeating units containing branched alkyl groups(which each preferably contain 4 to 20 carbon atoms), cycloalkyl groups(which each preferably contain 4 to 20 carbon atoms), branched alkenylgroups (which each preferably contain 4 to 20 carbon atoms),cycloalkenyl groups (which each preferably contain 4 to 20 carbon atoms)or aryl groups (which each preferably contain 4 to 20 carbon atoms),preferably a copolymer resin constituted of the repeating units (a), therepeating units (b) and the repeating units (c).

Into the repeating units (c) which are contained in each of the resins(X-3), (X-4) and (X-6) and have branched alkyl groups, cycloalkylgroups, branched alkenyl groups, cycloalkenyl groups or aryl groups,appropriate functional groups can be introduced with consideration givento a balance between hydrophilic and hydrophobic properties and mutualinteractivity.

(X-7): A resin that has (d) repeating units containing alkali-solublegroups (preferably repeating units containing alkali-soluble groupswhose pKa values are 4 or above) in addition to the repeating unitsconstituting each of the resins (X-1) to (X-6).

(X-8): A resin that has only the repeating units (d) whosealkali-soluble groups include fluorinated alcohol groups.

In the resins (X-3), (X-4), (X-6) and (X-7), the proportion of (a)repeating units containing fluoroalkyl groups, or the proportion of (b)repeating units containing trialkylsilyl groups or cyclic siloxanestructures, or the total proportion of the repeating units (a) and therepeating units (b) is preferably from 10 to 99 mole %, far preferablyfrom 20 to 80 mole %.

By having the alkali-soluble group-containing repeating units (d) in theresin (X-7), stripping by use of not only a negative developer but alsoother liquid removers, such as the case of using an alkaline aqueoussolution as liquid remover, becomes easier.

The Resin (X) is preferably in a solid state at room temperature (25°C.), and the glass transition temperature (Tg) thereof is preferablyfrom 50° C. to 200° C., far preferably from 80° C. to 160° C.

The expression “to be in a solid state at 25° C.” is intended to have amelting point of 25° C. or higher.

The glass transition temperature (Tg) can be measured with adifferential scanning calorimeter, and can be determined, e.g., byanalyzing specific volume variations occurring when a sample temperatureis raised once, then the sample is cooled, and further a temperaturerise at a rate of 5° C./min is carried out.

It is appropriate that the Resin (X) be insoluble in an immersion liquid(preferably water) but soluble in a negative developer (preferably adeveloper containing an organic solvent, far preferably a developercontaining an ester solvent). From the viewpoint of stripping-offcapabilities at the time of development with a positive developer, it ispreferable that the Resin (X) is also soluble in an alkali developer.

When Resin (X) contains silicon atoms, the silicon content therein ispreferably from 2 to 50 mass %, far preferably from 2 to 30 mass %, withrespect to the molecular weight of the Resin (X). And the proportion ofsilicon-containing repeating units in the Resin (X) is preferably from10 to 100 mass %, far preferably from 20 to 100 mass %.

Adjusting the silicon content and the proportion of silicon-containingrepeating units in Resin (X) to fall within the ranges specified aboveallows the Resin (X) to have each of improved insolubility in animmersion liquid (preferably water), greater easiness of protective filmstripping in the case of using a negative developer and improvedincompatibility with resist film.

When Resin (X) contains fluorine atoms, the fluorine content therein ispreferably from 5 to 80 mass %, far preferably from 10 to 80 mass %,with respect to the molecular weight of the Resin (X). And theproportion of fluorine-containing repeating units in the Resin (X) ispreferably from 10 to 100 mass %, far preferably from 30 to 100 mass %.

Adjusting the fluorine content and the proportion of fluorine-containingrepeating units in Resin (X) to fall within the ranges specified aboveallows the Resin (X) to have each of improved insolubility in animmersion liquid (preferably water), greater easiness of protective filmstripping in the case of using a negative developer and improvedincompatibility with resist film.

The weight average molecular weight of Resin (X) calculated in terms ofstandard polystyrene is preferably from 1,000 to 100,000, far preferablyfrom 1,000 to 50,000, further preferably from 2,000 to 15,000,particularly preferably from 3,000 to 15,000.

From the viewpoint of reducing elution from the protective film into animmersion liquid, it is only natural that the content of impurities,such as metal, in Resin (X) is low, and besides, the content of monomerresidues in Resin (X) is reduced preferably to 10 mass % or below, farpreferably to 5 mass % or below, further preferably to I mass % orbelow. In addition, the molecular weight distribution (Mw/Mn, referredto as polydispersity) of Resin (X) is adjusted preferably to a range of1 to 5, far preferably to a range of 1 to 3, further preferably to arange of 1 to 1.5.

Various products on the market can be utilized as Resin (X), and it isalso possible to synthesize Resin (X) according to a general method(e.g., radical polymerization). As examples of a general synthesismethod, there are known a batch polymerization method in whichpolymerization is carried out by dissolving monomer species and aninitiator in a solvent and heating them, and a drop polymerizationmethod in which a solution containing monomer species and an initiatoris added dropwise to a heated solvent over 1 to 10 hours. However, it ispreferred that the drop polymerization method be used. Examples of asolvent usable in the polymerization reaction include ethers, such astetrahydrofuran, 1,4-dioxane and diisopropyl ether; ketones, such asmethyl ethyl ketone and methyl isobutyl ketone; ester solvents, such asethyl acetate; amide solvents, such as dimethylformamide anddimethylacetamide; and solvents as described hereafter, which candissolve the present composition, such as propylene glycol monomethylether acetate, propylene glycol monomethyl ether and cyclohexanone.

The polymerization reaction is preferably carried out in an atmosphereof inert gas, such as nitrogen or argon. And the polymerization isinitiated using a commercially available radical initiator (e.g., anazo-type initiator or peroxide) as polymerization initiator. The radicalinitiator is preferably an azo-type initiator, and more specifically, anazo-type initiator having an ester group, a cyano group or a carboxylgroup.

Examples of such a preferred azo-type initiator includeazobisisobutyronitrile, azobisdimethylvaleronitrile and dimethyl2,2′-azobis(2-methylpropionate). It is also possible to use a chaintransfer agent as required. The concentration of reaction species isgenerally from 5 to 50 mass %, preferably from 20 to 50 mass %, farpreferably from 30 to 50 mass %, and the reaction temperature isgenerally from 10° C. to 150° C., preferably from 30° C. to 120° C., farpreferably from 60° C. to 100° C.

After the reaction is completed, the reaction product is allowed tostand and cooled to room temperature, and then subjected topurification. For the purification, a usual method is applicable, andexamples thereof include a liquid-liquid extraction method in whichresidual monomers and oligomeric components are eliminated by washingwith water or by combined use of appropriate solvents, a method ofperforming purification in a solution state, such as an ultrafiltrationmethod in which only components of molecular weight lower than aspecific value are extracted and eliminated, a reprecipitation method inwhich a resin solution is dripped into a poor solvent to result incoagulation of the resin and elimination of residual monomers and so on,and a method of performing purification in a solid state, such as amethod of washing filtered resin slurry with a poor solvent. Forinstance, the reaction solution is brought into contact with an at most10-fold, preferably 10- to 5-fold, volume of solvent (poor solvent) inwhich the resin is slightly soluble or insoluble, thereby precipitatingthe intended resin as a solid.

As the solvent used in the operation of precipitation or reprecipitationfrom a polymer solution (precipitation or reprecipitation solvent), anysolvent can serve so long as it is a poor solvent of the polymer. Andthe solvent to be used in such an operation can be selectedappropriately from the following poor solvents according to the kind ofthe polymer. Specifically, the poor solvents include hydrocarbons (suchas aliphatic hydrocarbons including pentane, hexane, heptane and octane;alicyclic hydrocarbons including cyclohexane and methylcyclohexane; andaromatic hydrocarbons including benzene, toluene and xylene);halogenated hydrocarbons (such as aliphatic halogenated hydrocarbonsincluding methylene chloride, chloroform and carbon tetrachloride; andaromatic halogenated hydrocarbons including chlorobenzene anddichlorobenzene); nitro compounds (such as nitromethane andnitroethane); nitriles (such as acetonitrile and benzonitrile); ethers(such as linear ethers including diethyl ether, diisopropyl ether anddimethoxyethane; and cyclic ethers including tetrahydrofuran anddioxane); ketones (such as acetone, methyl ethyl ketone and diisobutylketone); esters (such as ethyl acetate and butyl acetate); carbonates(such as dimethyl carbonate, diethyl carbonate, ethylene carbonate andpropylene carbonate); alcohols (such as methanol, ethanol, propanol,isopropyl alcohol and butanol); carboxylic acids (such as acetic acid);water: and mixed solvents containing the solvents recited above. Ofthese solvents, solvents containing at least alcohol (especiallymethanol) or water are preferred as precipitation or reprecipitationsolvents. In such a mixed solvent containing at least a hydrocarbon, theratio of alcohol (especially methanol) to other solvents (e.g., esterssuch as ethyl acetate, ethers such as tetrahydrofuran), thealcohol/other solvents ratio, by volume at 25° C. is preferably of theorder of 10/90 to 99/1, far preferably of the order of 30/70 to 98/2,further preferably of the order of 50/50 to 97/3.

The amount of a precipitation or reprecipitation solvent used can bechosen appropriately with consideration given to efficiency and yield,and it is generally from 100 to 10,000 parts by mass, preferably from200 to 2,000 parts by mass, far preferably from 300 to 1,000 parts bymass, per 100 parts by mass of polymer solution.

The bore of a nozzle used for feeding a polymer solution into aprecipitation or reprecipitation solvent (poor solvent) is preferably 4mmφ or below (e.g., 0.2 to 4 mmφ. And the linear speed at which apolymer solution is fed (dripped) into a poor solvent is, e.g., from 0.1to 10 msec, preferably of the order of 0.3 to 5 msec.

The precipitation or reprecipitation is preferably carried out withstirring. Examples of stirring blades usable for stirring include a deskturbine, a fan turbine (including paddles), a curved-blade turbine, afeather turbine, blades of Phaudler type, blades of Bullmargin type, anangle-blade fan turbine, propellers, multistage-type blades, anchor-type(horseshoe-type) blades, gate-type blades, double ribbon-type blades andscrews. It is preferable that the stirring is continued for additional10 minutes or above, especially 20 minutes or above, after the polymersolution feed is completed. When the stirring time is insufficient,there occurs a case where the monomer content in polymer particlescannot be reduced properly Instead of using stirring blades, a polymersolution and a poor solvent may be mixed together by using a line mixer.

The precipitation or reprecipitation temperature can be chosenappropriately with consideration given to efficiency and operationalease, and it is usually from 0° C. to 50° C., preferably in the vicinityof room temperature (e.g., from, 20° C. to 35° C.). In order to performthe precipitation or reprecipitation operation, a commonly-used mixingvessel, such as a stirred tank, and a hitherto known process, such as abatch process or a continuous process, can be utilized.

The polymer particles precipitated or reprecipitated are generallysubjected to solid-liquid separation, such as filtration orcentrifugation, and then dried. Thus, the polymer particles are madeavailable for use. The filtration is carried out using asolvent-resistant filtering material, preferably under a pressurizedcondition. The drying is performed at a temperature of the order of 30°C. to 100° C., preferably of the order of 30° C. to 50° C., under anormal pressure or a reduced pressure, preferably under a reducedpressure.

Additionally, resin once precipitated and separated out of its solutionmay be dissolved in a solvent again and brought into contact with asolvent in which the resin is slightly soluble or insoluble.

More specifically, it is acceptable to adopt a method which includesbringing a reaction solution after finishing radical polymerizationreaction into contact with a solvent in which the polymer produced isslightly soluble or insoluble, thereby precipitating the polymer asresin (process step a), separating the resin from the solution (processstep b), preparing a resin solution A by dissolving the resin in asolvent again (process step c), bringing the resin solution A intocontact with a solvent, in which the resin is slightly soluble orinsoluble, the volume of which is lower than 10 times, preferably nohigher than 5 times, the volume of the resin solution A, therebyprecipitating the resin as a solid (process step d), and separating theprecipitated resin out of the resultant solution (process step e).

The solvent used when the resin solution A is prepared may be a solventsimilar to the solvent used in dissolving monomer(s) for polymerizationreaction, and it may be one and the same as or different from thesolvent used in the polymerization reaction.

The protective film composition for use in the invention may furthercontain a surfactant.

The surfactant used has no particular restrictions, and any of anionicsurfactants, cationic surfactants and nonionic surfactants can be usedas long as they can ensure uniform film formation from the protectivefilm composition and are soluble in the solvent of the protective filmcomposition.

The amount of surfactants added is preferably from 0.001 to 20 mass %,far preferably from 0.01 to 10 mass %.

The surfactants may be used alone or as combinations of two or morethereof.

The surfactants suitable for use in the protective film composition canbe chosen from, e.g., alkyl cationic surfactants, amide-type quaternarycationic surfactants, ester-type quaternary cationic surfactants, amineoxide surfactants, betaine surfactants, alkoxylate surfactants, fattyacid ester surfactants, amide surfactants, alcohol surfactants,ethylenediamine surfactants, or fluorine- and/or silicon-containingsurfactants (fluorine-containing surfactants, silicon-containingsurfactants and surfactants containing both fluorine and silicon atoms).

Examples of the surfactants as recited above include polyoxyethylenealkyl ethers, such as polyoxyethylene lauryl ether, polyoxyethylenestearyl ether, polyoxyethylene cetyl ether and polyoxyethylene oleylether; polyoxyethylene alkyl aryl ethers, such as polyoxyethylene octylphenol ether and polyoxyethylene nonyl phenol ether;polyoxyethylene-polyooxypropylene block copolymers; sorbitan fatty acidesters, such as sorbitan monolaurate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan monooleate, sorbitan trioleate and sorbitantristearate; and polyoxyethylene sorbitan monolaurate, polyoxyethylenesorbitan monopalmitate, polyoxyethylene sorbitan monostearate,polyoxyethylene sorbitan trioleate and polyoxyethylene sorbitantristearate. In addition, commercial surfactants recited below can alsobe used as they are.

Examples of commercial surfactants which can be used include fluorine-or silicon-containing surfactants, such as EFTOP EF301 and EF303(produced by Shin-Akita Kasei K.K.), Florad FC430, 431 and 4430(produced by Sumitomo 3M, Inc.), Megafac F171, F173, F176, F189, F113,F110, F177, F120 and R08 (produced by Dainippon Ink & Chemicals, Inc.),Surflon S-382, SC101, 102, 103, 104, 105 and 106 (produced by AsahiGlass Co., Ltd.), Troysol S-366 (produced by Troy Chemical Industries,Inc.), GF-300 and GF-150 (produced by Toagosei Co., Ltd.), Surflon S-393(produced by Seimi Chemical Co., Ltd.), EFTOP EF121, EF122A, EF122B,RF122C, EF125M, EF135M, EF351, EF352, EF801, EF802 and EF601 (producedby JEMCO Inc.), PF636, PF656, PF6320 and PF6520 (produced by OMNOVASolutions Inc.), and FTX-204D, 208G, 218G, 230G, 204D, 208D, 212D, 218Dand 222D (produced by NEOS). In addition, organosiloxane polymer KP-341(produced by Shin-Etsu Chemical Co., Ltd.) can be used as asilicon-containing surfactant.

EXAMPLES

The invention is illustrated below in greater detail by reference to thefollowing examples, but these examples should not be construed aslimiting the scope of the invention.

Synthesis Example 1 Synthesis of Resin (X1)

In 250 ml of propylene glycol monomethyl ether, 43.6 g (0.1 mole) of4-[bis(trifluoromethyl)-hydroxymethyl]styrene is dissolved. To theresultant solution, 0.20 g of 2,2′-azobis(2,4-dimethylvaleronitrile)(V-65, trade name, a product of Wako Pure Chemical Industries, Ltd.) isadded as a polymerization initiator. This solution is stirred for 4hours at 70° C. in a stream of nitrogen. Thereafter, the reactionsolution is poured into IL of hexane with vigorous stirring. Resin thusprecipitated is washed with ion exchange water, filtered off, and driedin a vacuum. Thus, 39 g of white resin is obtained. The weight averagemolecular weight and polydispersity (Mw/Mn) of the thus obtained Resin(X1) are 7,500 and 1.65, respectively.

In the manners similar to the above, Resins (X2) to (X8) aresynthesized.

Structural formulae of Resins (X2) to (X8) are illustrated below. Theratio (by mole) between structural units, weight average molecularweight and polydispersity of each resin are summarized in Table 1.

<Preparation of Protective Film Composition>

Each combination of ingredients shown in Table 1 is dissolved in itscorresponding solvent shown in Table 1 in such an amount as to prepare asolution having a solids concentration of 2.5 mass %, and passed througha polyethylene filter having a pore size of 0.05 μm. Thereby, protectivefilm compositions Tx1 to Tx8 are prepared.

Evaluation of Solubility of Protective Film Composition in NegativeDeveloper:

On a 4-inch silicon wafer having undergone dehydration treatment withhexamethylsilazane, each of the protective film compositions shown inTable 1 is coated by means of a spin coater, and the coating solvent isdried by heating on a 120° C. hot plate for 60 seconds. Thus, 100nm-thick protective film is formed. Each of the thus formed films isimmersed in a 23° C. butyl acetate solution (negative developer) for aproper period of time, and a dissolution rate thereof is measured with aresist dissolution rate analyzer (RDA790, made by Litho Tech Japan Co.,Ltd.) and the rate of dissolution of each protective film composition inthe negative developer is calculated. Results obtained are shown inTable 1.

TABLE 1 Resin Ratio Weight Molecular Surfac- Disso- Protective betweenAverage Weight Solvent tant lution Film Structural Molecular Dispersity(weight (100 Rate Composition Code Units (mol %) Weight (Mw) (Mw/Mn)ratio) ppm) (nm/sec) Tx1 X1 100 7,500 1.65 SL-1 W-1 1 Tx2 X2 100 5,0001.75 SL-1 W-1 2 Tx3 X3 50/50 5,200 1.82 SL-1/ W-2 90 SL-2 (70/30) Tx4 X450/50 10,000 1.65 SL-1 W-3 6 Tx5 X5 50/50 16,000 1.85 SL-3 Not 1 addedTx6 X6 35/65 6,000 1.65 SL-1 W-2 10 Tx7 X7 50/50 5,500 1.63 SL-1 W-1 15Tx8 X8 70/30 4,200 1.71 SL-1 W-3 250

The symbols in Table 1 stand for the following compounds, respectively.

W-1: Megafac R08 (a surfactant containing both fluorine and siliconatoms, produced by Dainippon Ink & Chemicals, Inc.)

W-2: Organosiloxane polymer KP-341 (a silicon surfactant, produced byShin-Etsu Chemical Co., Ltd.)

W-3: PF6320 (a fluorinated surfactant, produced by OMNOVA SolutionsInc.)

SL-1:1-Butanol

SL-2: Perfluoro-2-butyltetrahydrofuran

SL-3: Propylene glycol monomethyl ether

Synthesis Example 2 Synthesis of Resin (A1)

In a stream of nitrogen, 20 g of 6:4 (by mass) solvent mixture ofpropylene glycol mnomethyl ether acetate and propylene glycol monomethylether is put in a three-necked flask and heated up to 80° C. (Solvent1). A monomer mixture composed of y-butyrolactone methacrylate,hydroxyadamantane methacrylate and 2-methyl-2-adamantyl methacrylate inproportions of 40:25:35 by mass is added to a 6:4 (by mass) solventmixture of propylene glycol mnomethyl ether acetate and propylene glycolmonomethyl ether, thereby preparing a 22 mass % monomer solution (200g). Further, an initiator V-601 (a product of Wako Pure ChemicalIndustries, Ltd.) is added to and dissolved in the monomer solution inan amount of 8 mol % based on the total monomers. The resultant solutionis added dropwise to the Solvent 1 over 6 hours. After the conclusion ofdropwise addition, reaction is made to continue at 80° C. for additional2 hours. The reaction solution obtained is allowed to stand for cooling.Then, the reaction solution is poured into a mixture of 1,800 ml ofhexane and 200 ml of ethyl acetate, and powdery matter thus precipitatedis filtered off and dried, thereby yielding 37 g of Resin (A1). Theweight average molecular weight and polydispersisty (Mw/Mn) of Resin(A1) thus obtained are 6,500 and 1.65, respectively.

In the manners similar to the above, Resins (A2) to (A8) aresynthesized.

Structural formulae of Resins (A2) to (A8) are illustrated below. Andthe ratio (by mole) between structural units, weight average molecularweight and polydispersity of each resin are summarized in Table 2.

<Preparation of Resist Composition>

Each combination of ingredients shown in Table 2 is dissolved in itscorresponding solvent shown in Table 2 in such an amount as to prepare asolution having a solids concentration of 6 mass %, and passed through apolyethylene filter having a pore size of 0.05 μm. Thereby, resistcompositions Ra1 to Ra8 are prepared.

TABLE 2 Resin Basic Acid Structure Ratio Com- Surfac- Generator (partsbetween pound tant Solvent Resist (parts by Mw Structural (parts (100(ratio by Composition by mass) mass) (Mw/Mn) Units (by mole) by mass)ppm) mass) Ra1 z62 A1 5,500 40/25/35 N-1 W-4 SL-5/SL-6 (5.0) (94.50)(1.65) (0.50) (70/30) Ra2 z57 A2 6,500 40/25/35 N-1 W-4 SL-5/SL-6 (5.0)(94.45) (1.65) (0.55) (70/30) Ra3 z59 A3 5,500 55/5/40 N-1 W-4 SL-5/SL-6(3.2) (96.30) (1.65) (0.50) (70/30) Ra4 z74 A4 8,200 55/5/40 N-2 W-3SL-5/SL-6 (4.5) (95.00) (1.68) (0.50) (60/40) Ra5 z76 A5 4,000 35/20/45N-2 W-2 SL-5/SL-6 (6.5) (93.05) (1.71) (0.45) (90/10) Ra6 z16 A6 8,50035/15/35/15 N-1 W-1 SL-5/SL-6 (5.0) (94.50) (1.85) (0.50) (80/20) Ra7 z8A7 13,500 40/5/45/10 N-3 W-4 SL-5/SL-6 (6.3) (93.30) (1.75) (0.40)(50/50) Ra8 z63 A8 5,500 40/10/40/10 N-1 W-4 SL-5/SL-6 (4.8) (94.70)(1.65) (0.50) (70/30)

The symbols in Table 2 stand for the following compounds, respectively.

N-1: N,N-Diphenylaniline

N-2: Diazabicyclo [4.3.0]nonene

N-3: 4-Dimethylaminopyridine

W-1: Megafac F176 (a fluorinated surfactant, produced by Dainippon Ink &Chemicals, Inc.)

W-2: Megafac R08 (a surfactant containing both fluorine and siliconatoms, produced by Dainippon Ink & Chemicals, Inc.)

W-3: Organosiloxane polymer KP-341 (a silicon surfactant, produced byShin-Etsu Chemical Co., Ltd.)

W-4: PF6320 (a fluorinated surfactant, produced by OMNOVA SolutionsInc.)

SL-5: Propylene glycol monomethyl ether acetate

SL-6: Propylene glycol monomethyl ether

By the methods mentioned hereinafter, evaluations are made using thethus prepared protective film compositions and resist compositions.

Example 1

An organic antireflective film ARC29A (a product of Nissan ChemicalIndustries, Ltd.) is applied to a silicon wafer surface, and baked at205° C. for 60 seconds, thereby forming a 78 nm-thick antireflectivefilm. On this film, the resist composition Ra1 is spin-coated, and bakedat 120° C. for 60 seconds, thereby forming a 150 nm-thick resist film.

Then, the protective film composition Tx1 is spin-coated on the resistfilm, and baked at 90° C. for 60 seconds, thereby forming a 30 nm-thickprotective film on the resist film.

The thus obtained wafer is subjected to immersion exposure via a maskfor pattern formation, wherein purified water is used as an immersionliquid and PAS5500/1250i equipped with a lens of NA=0.85 (made by ASML)is used as an ArF excimer laser scanner. After the exposure, the waferis spun at revs of 2,000 rpm, and thereby the water remaining on thewafer is removed. Then, the wafer is subjected successively to 60seconds' heating at 120° C., 60 seconds' development (negativedevelopment) with butyl acetate (negative developer), thereby undergoingsimultaneous removal of the protective film composition and solubleparts of the resist film, rinse with 1-hexanol, and 30 seconds' spinningat revs of 4,000 rpm. Thus, 150-nm (1:1) line-and-space resist patternsare formed.

Examples 2 to 8 and Comparative Example 1 Changes in Compositions ofResist Film and Protective Film

150-nm (1:1) Line-and-space patterns are formed in the same manner as inExample 1, except that the combination of resist and protective filmcompositions is changed to each of the combinations shown in Table 3.

Example 9 Carrying Out Negative Development after Positive development

An organic antireflective film ARC29A (a product of Nissan ChemicalIndustries, Ltd.) is applied to a silicon wafer surface, and baked at205° C. for 60 seconds, thereby forming a 78 nm-thick antireflectivefilm. On this film, the resist composition Ra1 is spin-coated, and bakedat 120° C. for 60 seconds, thereby forming a 150 nm-thick resist film.

Then, the protective film composition Tx1 is spin-coated on the resistfilm, and baked at 90° C. for 60 seconds, thereby forming a 30 nm-thickprotective film on the resist film.

The thus obtained wafer is subjected to immersion exposure via a maskfor pattern formation, wherein purified water is used as an immersionliquid and PAS5500/1250i equipped with a lens of NA=0.85 (made by ASML)is used as an ArF excimer laser scanner. After the exposure, the waterremaining on the wafer is removed by spinning the wafer at revs of 2,000rpm. Further, the wafer is heated at 120° C. for 60 seconds. Then, thewafer is subjected to 60 seconds' development (positive development)with an aqueous tetramethylammonium hydroxide solution (2.38 mass %)(positive developer), thereby undergoing simultaneous removal of theprotective film composition and soluble portions of the resist film, andfurther to rinse with purified water. Thus, patterns with a pitch of 600nm and a line width of 450 nm are formed. Next, the resultant wafer issubjected to 60 seconds' development (negative development) with butylacetate (negative developer), further to rinse with 1-hexanol, and thento 30 seconds' spinning at revs of 4,000 rpm. Thus, 150-nm (1:1)line-and-space resist patterns are obtained.

Example 10 Carrying Out Positive Development after Negative Development

An organic antireflective film ARC29A (a product of Nissan ChemicalIndustries, Ltd.) is applied to a silicon wafer surface, and baked at205° C. for 60 seconds, thereby forming a 78 nm-thick antireflectivefilm. On this film, the resist composition Ra1 is spin-coated, and bakedat 120° C. for 60 seconds, thereby forming a 150 nm-thick resist film.

Then, the protective film composition Tx1 is spin-coated on the resistfilm, and baked at 90° C. for 60 seconds, thereby forming a 30 nm-thickprotective film on the resist film.

The thus obtained wafer is subjected to immersion exposure via a maskfor pattern formation, wherein purified water is used as an immersionliquid and PAS5500/1250i equipped with a lens of NA=0.85 (made by ASML)is used as an ArF excimer laser scanner. After the exposure, the waterremaining on the wafer is removed by spinning the wafer at revs of 2,000rpm. Further, the wafer is heated at 120° C. for 60 seconds. Then, thewafer is subjected to 60 seconds' development (negative development)with butyl acetate (negative developer), thereby undergoing simultaneousremoval of the protective film composition and soluble portions of theresist film, further to rinse with 1-hexanol, and then to 30 seconds'spinning at revs of 4,000 rpm. Thus, patterns with a pitch of 600 nm anda line width of 450 nm are formed. Next, the resultant wafer issubjected to 60 seconds' development (positive development) with anaqueous tetramethylammonium hydroxide solution (2.38 mass %) (positivedeveloper), and further to rinse with purified water. Thus, 150-nm (1:1)line-and-space resist patterns are obtained.

Examples 11 to 20 and Comparative Examples 2 to 4 Change in DevelopmentCondition

150-nm (1:1) Line-and-space resist patterns are formed in the samemanner as in Example 1, except that the combination of protective filmcomposition, resist composition, negative developer and rinse liquid fornegative development is changed to each of the combinations shown inTable 3.

In Comparative Examples 2 to 4, on the other hand, positive developmentalone is carried out in place of negative development. Morespecifically, each wafer is subjected to 60 seconds' development(positive development) with an aqueous tetramethylammonium hydroxidesolution (2.38 mass %) (positive developer), thereby undergoingsimultaneous removal of the protective film composition and solubleportions of the resist film, further to rinse with purified water, andthen to 30 seconds' spinning at revs of 4,000 rpm.

Evaluation of Line Edge Roughness (LER)

A 150-nm (1:1) line-and-space pattern obtained in each of Examples 1 to20 and Comparative Examples 1 to 4 is observed under a criticaldimension scanning electron microscope (S-9260, made by Hitachi Ltd.),and the 150-nm line pattern is examined for distance from its edge linealong the length direction to a base line, on which the edge line shouldbe, at 50 different points on a 2-1.1m edge segment. And standarddeviation is determined from these distance measurements, and further 3ais calculated. The smaller the value thus calculated, the better theperformance. Results obtained are shown in Table 3.

Evaluation of Development Defect After Negative Development

Wafer processing is performed according to the same methods as inExamples 1 to 20 and Comparative Examples 1 to 4, respectively, whereinthe exposure is carried out so that 150-nm (1:1) line-and-space patternsare formed in 78 sections of each wafer plane. The total exposure areaof each wafer plane is 205 cm². The number of development defects ineach wafer with patterns is measured with a defect inspection systemKLA2360 (made by KLA-Tencor Corporation), and the value obtained bydividing the measured number by the exposure area is defined as thedevelopment defect number (number of defects/cm²). Results obtained areshown in Table 3.

Development defect numbers (number of defects/cm²) of 1 or below signifygood performance. More specifically, numeric values ranging from smallerthan 1 to 0.6 and those ranging from smaller than 0.6 to 0.2 are rankedin ascending order of performance improvement. And development defectnumbers greater than 1 signify poor performance.

TABLE 3 Protective Rinse liquid for Development Film Forming ResistNegative Developer Negative Development LER Defect CompositionComposition (ratio by mass) (ratio by mass) (nm) Number Example 1 Tx1Ra1 Butyl acetate 1-Hexanol 4.7 0.59 2 Tx2 Ra2 Butyl acetate 1-Hexanol5.4 0.50 3 Tx3 Ra3 Butyl acetate 1-Hexanol 3.5 0.29 4 Tx4 Ra4 Butylacetate 1-Hexanol 5.0 0.40 5 Tx5 Ra5 Butyl acetate 1-Hexanol 6.8 0.72 6Tx6 Ra6 Butyl acetate 1-Hexanol 3.9 0.28 7 Tx7 Ra7 Butyl acetate1-Hexanol 4.0 0.35 8 Tx8 Ra8 Butyl acetate 1-Hexanol 5.0 0.48 9 Tx1 Ra1Butyl acetate 1-Hexanol 7.1 0.76 10 Tx1 Ra1 Butyl acetate 1-Hexanol 3.30.41 11 Tx1 Ra1 Butyl acetate 3-Methyl-1-butanol 4.6 0.27 12 Tx2 Ra1Isoamyl acetate 1-Hexanol 3.2 0.23 13 Tx1 Ra1 Methyl isobutyl ketone1-Hexanol 6.9 0.50 14 Tx2 Ra1 2-Hexanone 1-Hexanol 5.0 0.49 15 Tx3 Ra1n-Butyl ether 1-Hexanol 4.3 0.32 16 Tx4 Ra1 Butyl acetate/2-Hexanone 1-Hexanol 5.4 0.45 (80/20) 17 Tx5 Ra1 Isoamyl acetate/n-Butyl ether1-Hexanol 5.2 0.75 (70/30) 18 Tx6 Ra1 Isoamyl acetate 2-Heptanol 3.10.25 19 Tx7 Ra1 Isoamyl acetate Decane 4.3 0.35 20 Tx8 Ra1 Isoamylacetate 2-Heptanol/Decane 5.1 0.55 (50/50) Comparative 1 Not used Ra1Butyl acetate 1-Hexanol 12.2 1.56 Example 2 Tx4 Ra1 — — 10.8 1.66 3 Tx5Ra1 — — 11.9 1.46 4 Tx6 Ra1 — — Absence of resolved pattern

The term “ratio by mass” as used in Table 3 means a mixture ratio bymass in the case of using two kinds of organic solvents in combinationas a negative developer or a rinse liquid for negative development.Herein, the ratio by mass in the case of using an organic solvent singlyas a negative developer or a rinse liquid for negative development is100.

The vapor pressures and boiling points of the solvents used asdevelopers and rinse liquids for negative development in Examples arelisted in Table 4.

TABLE 4 Vapor Pressure Solvent Name (kPa, value at 20° C.) Boiling Point(° C.) Butyl acetate 1.2 126 Isoamyl acetate 0.53 142 Methyl isobutylketone 2.1 117-118 2-Hexanone 0.36 126-128 Methyl ethyl ketone 10.5  80Dipropyl ether 8.33 88-90 n-Butyl ether 0.64 142 1-Hexanol 0.13 1571-Heptanol 0.015 175 2-Heptanol 0.133 150-160 3-Methyl-1-butanol 0.4 132Decane 0.17 174 Dodecane 0.04 216

As clearly seen from Examples, high-accuracy, fine patterns reduced inline edge roughness and prevented from causing development defect afterdevelopment can be formed consistently from the negative resistcompositions according to the invention.

According to the invention, it is possible to provide a method offorming patterns with high accuracy through the attainment of reductionin not only development defects appearing after development but alsoline edge roughness.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

1. A method for producing a semiconductor device, comprising a method offorming patterns, wherein the method of forming patterns comprises: (a)coating a substrate with a resist composition for negative developmentto form a resist film, wherein the resist composition contains a resincapable of increasing its polarity by the action of the an acid andbecomes more soluble in positive developer and less soluble in negativedeveloper upon irradiation with an actinic ray or radiation, (b) forminga protective film on the resist film with a protective film compositionafter forming the resist film and before exposing the resist film, (c)exposing the resist film via an immersion medium, and (d) performingdevelopment with a negative developer which consists essentially of anester solvent.
 2. The method for producing a semiconductor device ofclaim 1, wherein the process (d) of performing development comprises aprocess of removing the protective film composition and soluble portionsof the resist film at the same time.
 3. The method for producing asemiconductor device of claim 1, wherein the method of forming patternsfurther comprises: (e) performing development with a positive developer.4. The method for producing a semiconductor device of claim 1, whereinthe protective film has a rate of dissolution into the negativedeveloper in a range of 1 nm/sec to 300 nm/sec.
 5. The method forproducing a semiconductor device of claim 1, wherein the protective filmcomposition contains a resin having at least either a fluorine atom or asilicon atom.
 6. The method for producing a semiconductor device ofclaim 1, wherein the protective film composition contains a solventdifferent from the negative developer.
 7. The method for producing asemiconductor device of claim 1, wherein the ester solvent is selectedfrom the group consisting of butyl acetate, amyl acetate, andethyl-3-ethoxypropionate.
 8. A method for producing a semiconductordevice, comprising a method of forming patterns, wherein the method offorming patterns comprises: (a) coating a substrate with a resistcomposition for negative development to form a resist film, wherein theresist composition contains a resin capable of increasing its polarityby the action of the an acid and becomes more soluble in positivedeveloper and less soluble in negative developer upon irradiation withan actinic ray or radiation, (b) forming a protective film on the resistfilm with a protective film composition after forming the resist filmand before exposing the resist film, (c) exposing the resist film via animmersion medium, and (d) performing development with a negativedeveloper, wherein the negative developer comprises as least one solventselected from the group consisting of butyl acetate, amyl acetate, andethyl-3-ethoxypropionate.
 9. The method for producing a semiconductordevice of claim 8, wherein the process (d) of performing developmentcomprises a process of removing the protective film composition andsoluble portions of the resist film at the same time.
 10. The method forproducing a semiconductor device of claim 8, wherein the method offorming patterns further comprises: (e) performing development with apositive developer.
 11. The method for producing a semiconductor deviceof claim 8, wherein the protective film has a rate of dissolution intothe negative developer in a range of 1 nm/sec to 300 nm/sec.
 12. Themethod for producing a semiconductor device of claim 8, wherein theprotective film composition contains a resin having at least either afluorine atom or a silicon atom.
 13. The method for producing asemiconductor device of claim 8, wherein the protective film compositioncontains a solvent different from the negative developer.
 14. A methodfor producing a semiconductor device, comprising a method of formingpatterns, wherein the method of forming patterns comprises: (a) coatinga substrate with a resist composition for negative development to form aresist film, wherein the resist composition contains a resin capable ofincreasing its polarity by the action of the an acid and becomes moresoluble in positive developer and less soluble in negative developerupon irradiation with an actinic ray or radiation, (b) forming aprotective film on the resist film with a protective film compositionafter forming the resist film and before exposing the resist film, (c)exposing the resist film via an immersion medium, and (d) performingdevelopment with a negative developer consisting essentially of anorganic solvent having a boiling point of from 80° C. to 174° C.
 15. Themethod for producing a semiconductor device of claim 14, wherein theprocess (d) of performing development comprises a process of removingthe protective film composition and soluble portions of the resist filmat the same time.
 16. The method for producing a semiconductor device ofclaim 14, wherein the method of forming patterns further comprises: (e)performing development with a positive developer.
 17. The method forproducing a semiconductor device of claim 14, wherein the protectivefilm has a rate of dissolution into the negative developer in a range of1 nm/sec to 300 nm/sec.
 18. The method for producing a semiconductordevice of claim 14, wherein the protective film composition contains aresin having at least either a fluorine atom or a silicon atom.
 19. Themethod for producing a semiconductor device of claim 14, wherein theprotective film composition contains a solvent different from thenegative developer.
 20. A method for producing a semiconductor device,comprising a method of forming patterns, wherein the method of formingpatterns comprises: coating a resist composition for negativedevelopment to form a resist film, wherein the resist compositioncontains a resin capable of increasing its polarity by the action of anacid and becomes more soluble in a positive developer which is an alkalideveloper and less soluble in a negative developer containing an organicsolvent upon irradiation with an actinic ray or radiation, forming aprotective film on the resist film with a protective film compositionafter forming the resist film and before exposing the resist film,exposing the resist film containing the protective film via an immersionmedium, and performing development with the negative developer.
 21. Themethod for producing a semiconductor device of claim 20, wherein theprotective film composition and soluble portions of the resist film areremoved at the same time by the development using the negativedeveloper.
 22. The method for producing a semiconductor device of claim20, comprising: developing the resist film after exposure by using thepositive developer at least either after or before the development usingthe negative developer.
 23. The method for producing a semiconductordevice of claim 20, wherein a rate of dissolution of the protective filmcomposition into the negative developer after film formation is in arange of 1 nm/sec to 300 nm/sec.
 24. The method for producing asemiconductor device of claim 20, wherein the protective filmcomposition contains a resin having at least either a fluorine atom or asilicon atom.
 25. The method for producing a semiconductor device ofclaim 20, wherein the protective film composition contains a solventdifferent from the negative developer in component.
 26. The method forproducing a semiconductor device of claim 20, wherein the organicsolvent which the negative developer contains is at least one organicsolvent selected from the group consisting of a ketone solvent, an estersolvent or an ether solvent.
 27. The method for producing asemiconductor device of claim 20, wherein the method of forming patternscomprises cleaning using an organic solvent-containing rinse liquidafter the development using the negative developer.
 28. The method forproducing a semiconductor device of claim 27, the organic solvent whichthe rinse liquid contains is an alcohol solvent.
 29. The method forproducing a semiconductor device of claim 20, wherein the immersionmedium is water.
 30. The method for producing a semiconductor device ofclaim 20, wherein the resin capable of increasing the polarity by theaction of the acid is a resin having mononuclear or polynuclearalicyclic hydrocarbon structure.
 31. The method for producing asemiconductor device of claim 20, wherein the resin capable ofincreasing the polarity by the action of the acid is a resin having noaromatic group.
 32. The method for producing a semiconductor device ofclaim 26, wherein the organic solvent which the negative developercontains is a ketone solvent.
 33. The method for producing asemiconductor device of claim 26, wherein the organic solvent which thenegative developer contains is an ester solvent.
 34. The method forproducing a semiconductor device of claim 26, wherein the organicsolvent which the negative developer contains is an ether solvent. 35.The method for producing a semiconductor device of claim 30, wherein theresin is an alicyclic hydrocarbon-containing acid-decomposable resinhaving a repeating unit having an alicyclic hydrocarbon-containingpartial structure represented by any of the following formula (pI) or(pII):

wherein R₁₁ represents a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group or asec-butyl group, and Z represents atoms forming a cycloalkyl grouptogether with the carbon atom; R₁₂ to R₁₄ each represent astraight-chain or branched alkyl group having 1 to 4 carbon atom(s), ora cycloalkyl group independently, provided that at least one of R₁₂ toR₁₄ represents a cycloalkyl group.
 36. The method for producing asemiconductor device of claim 35, wherein the repeating unit is arepeating unit represented by the following formula (pA):

wherein each R represents a hydrogen atom, a halogen atom or astraight-chain or branched alkyl group having 1 to 4 carbon atom(s), twoor more Rs may be the same or different, A represents a single bond, analkylene group, an ether group, a thioether group, a carbonyl group, anester group, an amido group, a sulfonamido group, a urethane group, aurea group, or a combination of two or more of the groups recited above,and Rp₁ represents any of the formula (pI) or (pII).
 37. The method forproducing a semiconductor device of claim 24, wherein the protectivefilm composition contains a resin having a fluorine atom.
 38. The methodfor producing a semiconductor device of claim 24, wherein the protectivefilm composition contains a resin having a silicon atom.
 39. The methodfor producing a semiconductor device of claim 20, wherein the exposureis performed using ArF excimer laser light.